Code Mode: give agents an entire API in 1,000 tokens (opens in new tab)
Code Mode addresses a central MCP problem: giving agents broad tool access without overwhelming their context windows. Instead of exposing thousands of individually described tools, it provides a typed SDK and lets agents write sandboxed JavaScript to search specifications and execute API calls. Cloudflare’s new MCP server applies this approach to its entire API using only `search()` and `execute()`, reducing context usage by 99.9% to roughly 1,000 tokens. ## The Context-Window Problem - MCP makes external tools available to AI agents, but each tool’s description consumes model context. - Large APIs can require enormous token budgets merely to describe their endpoints. - A conventional MCP server for the Cloudflare API would consume approximately 1.17 million tokens. - This can exceed the context window of even advanced foundation models. ## Code Mode as a Compact API Interface - Agents write code against a typed SDK rather than selecting from thousands of separate tools. - Generated code serves as a compact, composable plan. - Agents can: - Explore available operations. - Chain multiple API calls. - Handle pagination and errors. - Return only the data needed for the task. - The tool footprint remains fixed as the underlying API grows. ## Cloudflare’s Two-Tool MCP Server - The server exposes only: - `search()` — searches the Cloudflare OpenAPI specification. - `execute()` — runs JavaScript against the Cloudflare API. - The full OpenAPI specification stays outside the model context. - `$refs` are pre-resolved, allowing agents to inspect endpoint metadata directly through code. - Agents can filter endpoints by product, path, tags, or other metadata. ## Sandboxed Execution - Both tools execute code inside a Dynamic Worker isolate based on lightweight V8 sandboxes. - The environment has: - No filesystem access. - No environment variables exposed to generated code. - External fetches disabled by default. - Outbound requests can be explicitly enabled through controlled fetch handlers. ## Example: Finding DDoS Protection Endpoints - For a request to protect an origin from DDoS attacks, an agent can first consult documentation or skills. - It then uses `search()` to inspect the OpenAPI specification. - A JavaScript query can locate zone endpoints related to WAF and rulesets. - The search narrows more than 2,500 Cloudflare endpoints to relevant operations such as: - Listing and updating WAF packages and rules. - Listing and creating zone rulesets. - Reading and updating entry-point rulesets. - Creating and updating rules within a ruleset. - Once the relevant endpoints are identified, `execute()` can perform coordinated API requests in one sandboxed run. ## SDK Availability - Cloudflare is open-sourcing a Code Mode SDK as part of the Cloudflare Agents SDK. - The same pattern can be used to build more context-efficient MCP servers and AI agents. Code Mode is most useful for large, evolving APIs: expose a small, stable tool surface, let agents discover capabilities programmatically, and execute only the focused operations required for each task.