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Generate types from your tools

The problem

Section titled “The problem”

Your UI calls MCP tools, but the tool schemas live on the server. If you hand-write the input and output types in the UI, they drift the moment the server changes a field, and TypeScript cannot catch the mismatch. You want the types generated straight from the source of truth.

The recipe

Section titled “The recipe”

Run the synapse codegen CLI against whichever source you have. From an app manifest:

Terminal window
npx synapse codegen --from-manifest ./manifest.json --out src/generated/types.ts

From a running MCP server (it calls tools/list over HTTP):

Terminal window
npx synapse codegen --from-server http://localhost:3000/mcp --out src/generated/types.ts

From a directory of .schema.json entity files (generates CRUD tool types):

Terminal window
npx synapse codegen --from-schema ./schemas --out src/generated/types.ts

How it works

Section titled “How it works”

For every tool, codegen emits a PascalCase XxxInput interface from the tool’s input schema and, when the tool declares an output schema, a matching XxxOutput interface (tools with no output schema map to unknown). It then emits one AppToolMap interface, named from your app, that maps each tool name to its input and output types. That map is what gives a typed useCallTool the right argument and result types per tool.

--from-schema is the exception that generates tools rather than reading them. Each <entity>.schema.json file becomes a full CRUD set: create_<entity>, read_<entity>, update_<entity>, delete_<entity>, and list_<entity>s, each with input and output types derived from the entity schema.

A few flags worth knowing: --out defaults to src/generated/types.ts, and --app overrides the app name used to name the tool map (with --from-manifest it defaults to the manifest’s name). Re-run the command whenever the server’s tools change, and commit the generated file or wire the command into your build.

Section titled “Related”