Code Mode: the better way to use MCP

It turns out we've all been using MCP wrong.

Most agents today use MCP by directly exposing the "tools" to the LLM.

We tried something different: Convert the MCP tools into a TypeScript API, and then ask an LLM to write code that calls that API.

The results are striking:

  1. We found agents are able to handle many more tools, and more complex tools, when those tools are presented as a TypeScript API rather than directly. Perhaps this is because LLMs have an enormous amount of real-world TypeScript in their training set, but only a small set of contrived examples of tool calls.

  2. The approach really shines when an agent needs to string together multiple calls. With the traditional approach, the output of each tool call must feed into the LLM's neural network, just to be copied over to the inputs of the next call, wasting time, energy, and tokens. When the LLM can write code, it can skip all that, and only read back the final results it needs.

In short, LLMs are better at writing code to call MCP, than at calling MCP directly.

What's MCP?

For those that aren't familiar: Model Context Protocol is a standard protocol Continue reading

Eliminating Cold Starts 2: shard and conquer

Five years ago, we announced that we were Eliminating Cold Starts with Cloudflare Workers. In that episode, we introduced a technique to pre-warm Workers during the TLS handshake of their first request. That technique takes advantage of the fact that the TLS Server Name Indication (SNI) is sent in the very first message of the TLS handshake. Armed with that SNI, we often have enough information to pre-warm the request’s target Worker.

Eliminating cold starts by pre-warming Workers during TLS handshakes was a huge step forward for us, but “eliminate” is a strong word. Back then, Workers were still relatively small, and had cold starts constrained by limits explained later in this post. We’ve relaxed those limits, and users routinely deploy complex applications on Workers, often replacing origin servers. Simultaneously, TLS handshakes haven’t gotten any slower. In fact, TLS 1.3 only requires a single round trip for a handshake – compared to three round trips for TLS 1.2 – and is more widely used than it was in 2021.

Earlier this month, we finished deploying a new technique intended to keep pushing the boundary on cold start reduction. The new technique (or old, depending on your perspective) uses Continue reading

Network performance update: Birthday Week 2025

We are committed to being the fastest network in the world because improvements in our performance translate to improvements for the own end users of your application. We are excited to share that Cloudflare continues to be the fastest network for the most peered networks in the world.

We relentlessly measure our own performance and our performance against peers. We publish those results routinely, starting with our first update in June 2021 and most recently with our last post in September 2024.

Today’s update breaks down where we have improved since our update last year and what our priorities are going into the next year. While we are excited to be the fastest in the greatest number of last-mile ISPs, we are never done improving and have more work to do.

How do we measure this metric, and what are the results?

We measure network performance by attempting to capture what the experience is like for Internet users across the globe. To do that we need to simulate what their connection is like from their last-mile ISP to our networks.

We start by taking the 1,000 largest networks in the world based on estimated population. We use that to give Continue reading

Ultra Ethernet: Fabric Creation Process in Libfabric

[edit Oct-8, 2025]
New version of this subject can be found here: Ultra Ethernet: Fabric Object - What it is and How it is created

Phase 1: Application (Discovery & choice)

After the UET provider populated fi_info structures for each NIC/port combination during discovery, the application can begin the object creation process. It first consults the in-memory fi_info list to identify the entry that best matches its requirements. Each fi_info contains nested attribute structures describing fabric, domain, and endpoint capabilities, including fi_fabric_attr (fabric name, provider identifier, version information), fi_domain_attr (memory registration mode, key details, domain capabilities), and fi_ep_attr (endpoint type, reliable versus unreliable semantics, size limits, and supported capabilities). The application examines the returned entries and selects the fi_info that satisfies its needs (for example: provider == "uet", fabric name == "UET", required capabilities, reliable transport, or a specific memory registration mode). The chosen fi_info then provides the attributes — effectively serving as hints — that the application passes into subsequent creation calls such as fi_fabric(), fi_domain(), and fi_endpoint(). Each fi_info acts as a self-contained “capability snapshot,” describing one possible combination of NIC, port, and transport mode.


Phase 2: Libfabric Core (dispatch & wiring)

When the application calls fi_fabric(), the Continue reading

How Cloudflare uses the world’s greatest collection of performance data to make the world’s fastest global network even faster

Cloudflare operates the fastest network on the planet. We’ve shared an update today about how we are overhauling the software technology that accelerates every server in our fleet, improving speed globally.

That is not where the work stops, though. To improve speed even further, we have to also make sure that our network swiftly handles the Internet-scale congestion that hits it every day, routing traffic to our now-faster servers.

We have invested in congestion control for years. Today, we are excited to share how we are applying a superpower of our network, our massive Free Plan user base, to optimize performance and find the best way to route traffic across our network for all our customers globally.

Early results have seen performance increases that average 10% faster than the prior baseline. We achieved this by applying different algorithmic methods to improve performance based on the data we observe about the Internet each day. We are excited to begin rolling out these improvements to all customers.

How does traffic arrive in our network?

The Internet is a massive collection of interconnected networks, each composed of many machines (“nodes”). Data is transmitted by breaking it up into small packets, and passing them Continue reading

Lab: Protect IS-IS Routing Data with MD5 Authentication

Like OSPF and BGP, IS-IS contains a simple mechanism to authenticate routing traffic – IS-IS packets can include a cleartext password or an MD5- or SHA hash. Unlike OSPF, IS-IS can also authenticate:

  • The hello packets exchanged between routers
  • The contents of Link State PDUs flooded across an area or a domain.

Want to know more? Check out the Protect IS-IS Routing Data with MD5 Authentication lab exercise.

Click here to start the lab in your browser using GitHub Codespaces (or set up your own lab infrastructure). After starting the lab environment, change the directory to feature/3-md5 and execute netlab up.

Dicing, Slicing, And Augmenting Gartner’s AI Spending Forecast

When we try to predict the weather, we use ensembles of the initial conditions on the ground, in the oceans, and throughout the air to create a kind of probabilistic average forecast and then we take ensembles of models, which often have very different answers for extreme weather conditions like hurricanes and typhoons, to get a better sense of what might happen wherever and whenever we are concerned. …

Dicing, Slicing, And Augmenting Gartner’s AI Spending Forecast was written by Timothy Prickett Morgan at The Next Platform.

IPB184: IPv6 Basics: Dual-Stack

We’re diving into another IPv6 Basics today with the topic of dual-stack, which means running the IPv4 and IPv6 protocol stacks simultaneously. We get many questions about the implications of running dual-stack, and in this episode we’ll provide answers. We start by getting a little finicky about the definition of dual-stack, and then talk about... Read more »

Cloudflare’s developer platform keeps getting better, faster, and more powerful. Here’s everything that’s new.

When you build on Cloudflare, we consider it our job to do the heavy lifting for you. That’s been true since we introduced Cloudflare Workers in 2017, when we first provided a runtime for you where you could just focus on building. 

That commitment is still true today, and many of today’s announcements are focused on just that — removing friction where possible to free you up to build something great. 

There are only so many blog posts we can write (and that you can read)! We have been busy on a much longer list of new improvements, and many of them we’ve been rolling out consistently over the course of the year. Today’s announcement breaks down all the new capabilities in detail, in one single post. The features being released today include:

Partnering to make full-stack fast: deploy PlanetScale databases directly from Workers

We’re not burying the lede on this one: you can now connect Cloudflare Workers to your PlanetScale databases directly and ship full-stack applications backed by Postgres or MySQL. 

We’ve teamed up with PlanetScale because we wanted to partner with a database provider that we could confidently recommend to our users: one that shares our obsession with performance, reliability and developer experience. These are all critical factors for any development team building a serious application. 

Now, when connecting to PlanetScale databases, your connections are automatically configured for optimal performance with Hyperdrive, ensuring that you have the fastest access from your Workers to your databases, regardless of where your Workers are running.

Building full-stack

As Workers has matured into a full-stack platform, we’ve introduced more options to facilitate your connectivity to data. With Workers KV, we made it easy to store configuration and cache unstructured data on the edge. With D1 and Durable Objects, we made it possible to build multi-tenant apps with simple, isolated SQL databases. And with Hyperdrive, we made connecting to external databases fast and scalable from Workers.

Today, we’re introducing a new choice for building on Cloudflare: Postgres and MySQL PlanetScale databases, directly Continue reading

R2 SQL: a deep dive into our new distributed query engine

How do you run SQL queries over petabytes of data… without a server?

We have an answer for that: R2 SQL, a serverless query engine that can sift through enormous datasets and return results in seconds.

This post details the architecture and techniques that make this possible. We'll walk through our Query Planner, which uses R2 Data Catalog to prune terabytes of data before reading a single byte, and explain how we distribute the work across Cloudflare’s global network, Workers and R2 for massively parallel execution.

From catalog to query

During Developer Week 2025, we launched R2 Data Catalog, a managed Apache Iceberg catalog built directly into your Cloudflare R2 bucket. Iceberg is an open table format that provides critical database features like transactions and schema evolution for petabyte-scale object storage. It gives you a reliable catalog of your data, but it doesn’t provide a way to query it.

Until now, reading your R2 Data Catalog required setting up a separate service like Apache Spark or Trino. Operating these engines at scale is not easy: you need to provision clusters, manage resource usage, and be responsible for their availability, none of which contributes to the primary goal of Continue reading

Safe in the sandbox: security hardening for Cloudflare Workers

As a serverless cloud provider, we run your code on our globally distributed infrastructure. Being able to run customer code on our network means that anyone can take advantage of our global presence and low latency. Workers isn’t just efficient though, we also make it simple for our users. In short: You write code. We handle the rest.

Part of 'handling the rest' is making Workers as secure as possible. We have previously written about our security architecture. Making Workers secure is an interesting problem because the whole point of Workers is that we are running third party code on our hardware. This is one of the hardest security problems there is: any attacker has the full power available of a programming language running on the victim's system when they are crafting their attacks.

This is why we are constantly updating and improving the Workers Runtime to take advantage of the latest improvements in both hardware and software. This post shares some of the latest work we have been doing to keep Workers secure.

Some background first: Workers is built around the V8 JavaScript runtime, originally developed for Chromium-based browsers like Chrome. This gives us a head start, because V8 Continue reading

Every Cloudflare feature, available to everyone

Over the next year Cloudflare will make nearly every feature we offer available to any customer who wants to buy and use it regardless of whether they are an enterprise account. No need to pick up a phone and talk to a sales team member. No requirement to find time with a solutions engineer in our team to turn on a feature. No contract necessary. We believe that if you want to use something we offer, you should just be able to buy it.

Today’s launch starts by bringing Single Sign-On (SSO) into our dashboard out of our enterprise plan and making it available to any user. That capability is the first of many. We will be sharing updates over the next few months as more and more features become available for purchase on any plan.

We are also making a commitment to ensuring that all future releases will follow this model. The goal is not to restrict new tools to the enterprise tier for some amount of time before making them widely available. We believe helping build a better Internet means making sure the best tools are available to anyone who needs them.

Enterprise grade for everyone

It’s not Continue reading

Choice: the path to AI sovereignty

Every government is laser-focused on the potential for national transformation by AI. Many view AI as an unparalleled opportunity to solve complex national challenges, drive economic growth, and improve the lives of their citizens. Others are concerned about the risks AI can bring to its society and economy. Some sit somewhere between these two perspectives. But as plans are drawn up by governments around the world to address the question of AI development and adoption, all are grappling with the critical question of sovereignty — how much of this technology, mostly centered in the United States and China, needs to be in their direct control? 

Each nation has their own response to that question — some seek ‘self-sufficiency’ and total authority. Others, particularly those that do not have the capacity to build the full AI technology stack, are approaching it layer-by-layer, seeking to build on the capacities their country does have and then forming strategic partnerships to fill the gaps. 

We believe AI sovereignty at its core is about choice. Each nation should have the ability to select the right tools for the task, to control its own data, and to deploy applications at will, all without being Continue reading

Announcing the Cloudflare Data Platform: ingest, store, and query your data directly on Cloudflare

For Developer Week in April 2025, we announced the public beta of R2 Data Catalog, a fully managed Apache Iceberg catalog on top of Cloudflare R2 object storage. Today, we are building on that foundation with three launches:

  • Cloudflare Pipelines receives events sent via Workers or HTTP, transforms them with SQL, and ingests them into Iceberg or as files on R2

  • R2 Data Catalog manages the Iceberg metadata and now performs ongoing maintenance, including compaction, to improve query performance

  • R2 SQL is our in-house distributed SQL engine, designed to perform petabyte-scale queries over your data in R2

Together, these products make up the Cloudflare Data Platform, a complete solution for ingesting, storing, and querying analytical data tables.

Like all Cloudflare Developer Platform products, they run on our global compute infrastructure. They’re built around open standards and interoperability. That means that you can bring your own Iceberg query engine — whether that's PyIceberg, DuckDB, or Spark — connect with other platforms like Databricks and Snowflake — and pay no egress fees to access your data.

Analytical data is critical for modern companies. It allows you to understand your user’s behavior, your company’s performance, and alerts you to issues. Continue reading

Announcing Cloudflare Email Service’s private beta

If you are building an application, you rely on email to communicate with your users. You validate their signup, notify them about events, and send them invoices through email. The service continues to find new purpose with agentic workflows and other AI-powered tools that rely on a simple email as an input or output.

And it is a pain for developers to manage. It’s frequently the most annoying burden for most teams. Developers deserve a solution that is simple, reliable, and deeply integrated into their workflow. 

Today, we're excited to announce just that: the private beta of Email Sending, a new capability that allows you to send transactional emails directly from Cloudflare Workers. Email Sending joins and expands our popular Email Routing product, and together they form the new Cloudflare Email Service — a single, unified developer experience for all your email needs.

With Cloudflare Email Service, we’re distilling our years of experience securing and routing emails, and combining it with the power of the developer platform. Now, sending an email is as easy as adding a binding to a Worker and calling send:

export default {
  async fetch(request, env, ctx) {

    await env.SEND_EMAIL.send({
      to: [{  Continue reading

N4N039: Configuring an IPsec Tunnel

We dive back into the world of IPsec with an episode dedicated to configuring IPsec tunnels. After discussing a listener comment regarding transport mode in IPsec tunnels, Ethan Banks and Holly Metlitzky work through topics such as multi-vendor IPsec configuration, licensing, and the details of configuration and routing. Bonus material: MTU size and NAT-T. Episode... Read more »

A year of improving Node.js compatibility in Cloudflare Workers

We've been busy.

Compatibility with the broad JavaScript developer ecosystem has always been a key strategic investment for us. We believe in open standards and an open web. We want you to see Workers as a powerful extension of your development platform with the ability to just drop code in that Just Works. To deliver on this goal, the Cloudflare Workers team has spent the past year significantly expanding compatibility with the Node.js ecosystem, enabling hundreds (if not thousands) of popular npm modules to now work seamlessly, including the ever popular express framework.

We have implemented a substantial subset of the Node.js standard library, focusing on the most commonly used, and asked for, APIs. These include:

Each of these has been carefully implemented to approximate Node.js' behavior as closely as possible where feasible. Where matching Node.js' behavior is not possible, our implementations will throw a clear error Continue reading

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