docs: add AGENTS.md and CONTRIBUTING.md (#194)
* docs: add AGENTS.md and CONTRIBUTING.md Codifies scenario design guidelines from past PR reviews: - fewer scenarios with more checks (CI cost multiplies per-SDK) - same check id for SUCCESS and FAIL, optimize for Ctrl+F - extend the everything-client/server rather than adding new example files - prove it passes and fails - reuse the CLI runner, don't add parallel entry points Also asks contributors to open an issue for discussion before a PR, and to target specific spec MUSTs or open issues rather than running generic AI bug-hunts against the harness. * docs: broaden issue-first guidance to cover bugs, not just scenarios
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Paul Carleton
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AGENTS.md
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AGENTS.md
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# AGENTS.md
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Guidance for AI agents (and humans) contributing to the MCP conformance test framework.
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## What this repo is
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A test harness that exercises MCP SDK implementations against the protocol spec. The coverage number that matters here is **spec coverage** — how much of the protocol the scenarios test.
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Uses **npm** (not pnpm/yarn). Don't commit `pnpm-lock.yaml` or `yarn.lock`.
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## Where to start
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**Open an issue first** — whether you've hit a bug in the harness or want to propose a new scenario. For scenarios, sketch which part of the spec you want to cover and roughly how; for bugs, include the command you ran and the output. Either way, a short discussion up front beats review churn on a PR that overlaps existing work or heads in a direction we're not going.
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**Don't point an agent at the repo and ask it to "find bugs."** Generic bug-hunting on a test harness produces low-signal PRs (typo fixes, unused-variable cleanups, speculative refactors). If you want to contribute via an agent, give it a concrete target:
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- Pick a specific MUST or SHOULD from the [MCP spec](https://modelcontextprotocol.io/specification/) that has no scenario yet, and ask the agent to draft one.
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- Pick an [open issue](https://github.com/modelcontextprotocol/conformance/issues) and work on that.
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The valuable contribution here is **spec coverage**, not harness polish.
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## Scenario design: fewer scenarios, more checks
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**The strongest rule in this repo:** prefer one scenario with many checks over many scenarios with one check each.
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Why:
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- Each scenario often spins up its own HTTP server. These suites run in CI on every push for every SDK, so per-scenario overhead multiplies fast.
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- Less code to maintain and update when the spec shifts.
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- Progress on making an SDK better shows up as "pass 7/10 checks" rather than "pass 1 test, fail another" — finer-grained signal from the same run.
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### Granularity heuristic
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Ask: **"Would it make sense for someone to implement a server/client that does just this scenario?"**
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If two scenarios would always be implemented together, merge them. Examples:
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- `tools/list` + a simple `tools/call` → one scenario
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- All content-type variants (image, audio, mixed, resource) → one scenario
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- Full OAuth flow with token refresh → one scenario, not separate "basic" + "refresh" scenarios. A client that passes "basic" but not "refresh" just shows up as passing N−2 checks.
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Keep scenarios separate when they're genuinely independent features or when they're mutually exclusive (e.g., an SDK should support writing a server that _doesn't_ implement certain stateful features).
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### When a PR adds scenarios
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- Start with **one end-to-end scenario** covering the happy path with many checks along the way.
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- Don't add "step 1 only" and "step 1+2" as separate scenarios — the second subsumes the first.
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- Register the scenario in the appropriate suite list in `src/scenarios/index.ts` (`core`, `extensions`, `backcompat`, etc.).
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## Check conventions
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- **Same `id` for SUCCESS and FAIL.** A check should use one slug and flip `status` + `errorMessage`, not branch into `foo-success` vs `foo-failure` slugs.
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- **Optimize for Ctrl+F on the slug.** Repetitive check blocks are fine — easier to find the failing one than to unwind a clever helper.
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- Reuse `ConformanceCheck` and other types from `src/types.ts` rather than defining parallel shapes.
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- Include `specReferences` pointing to the relevant spec section.
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## Descriptions and wording
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Be precise about what's **required** vs **optional**. A scenario description that tests optional behavior should make that clear — e.g. "Tests that a client _that wants a refresh token_ handles offline_access scope…" not "Tests that a client handles offline_access scope…". Don't accidentally promote a MAY/SHOULD to a MUST in the prose.
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When in doubt about spec details (OAuth parameters, audiences, grant types), check the actual spec in `modelcontextprotocol` rather than guessing.
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## Examples: prove it passes and fails
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A new scenario should come with:
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1. **A passing example** — usually by extending `examples/clients/typescript/everything-client.ts` or the everything-server, not a new file.
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2. **Evidence it fails when it should** — ideally a negative example (a deliberately broken client), or at minimum a manual run showing the failure mode.
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Delete unused example scenarios. If a scenario key in the everything-client has no corresponding test, remove it.
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## Don't add new ways to run tests
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Use the existing CLI runner (`npx @modelcontextprotocol/conformance client|server ...`). If you need a feature the runner doesn't have, add it to the runner rather than building a parallel entry point.
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## Before opening a PR
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- `npm run build` passes
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- `npm test` passes
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- For non-trivial scenario changes, run against at least one real SDK (typescript-sdk or python-sdk) to see actual output. For changes to shared infrastructure (runner, tier-check), test against go-sdk or csharp-sdk too.
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- Scenario is registered in the right suite in `src/scenarios/index.ts`
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CONTRIBUTING.md
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CONTRIBUTING.md
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# Contributing
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Thanks for helping improve the MCP conformance suite!
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The most valuable contributions are **new conformance scenarios** that cover under-tested parts of the [MCP spec](https://modelcontextprotocol.io/specification/). If you're not sure where to start, ask in `#conformance-testing-wg` on the MCP Contributors Discord.
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## Before you start
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**Open an issue first** — whether you've found a bug or want to propose a new scenario. A short discussion up front saves everyone time on PRs that overlap existing work or head in a direction we're not going.
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Then read **[AGENTS.md](./AGENTS.md)** — it's the design guide for scenarios and checks. The short version:
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- **Fewer scenarios, more checks.** Each scenario spins up its own server and runs in CI for every SDK. One scenario with 10 checks beats 10 scenarios with one check each.
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- **Prove it passes and fails.** Extend the existing everything-client/server to pass your scenario, and show (or include) a failing case.
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- **Reuse the CLI runner.** Don't add parallel entry points.
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If you're using an AI agent to help, please **don't** point it at the repo with a generic "find bugs" prompt — give it a specific MUST from the spec or an open issue to work on. See AGENTS.md for details.
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## Setup
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```sh
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npm install
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npm run build
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npm test
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```
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This repo uses **npm** — don't commit `pnpm-lock.yaml` or `yarn.lock`.
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## Running your scenario
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```sh
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# Against the bundled TypeScript example
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npm run build
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node dist/index.js client --command "tsx examples/clients/typescript/everything-client.ts" --scenario <your-scenario>
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# Against a server
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node dist/index.js server --url http://localhost:3000/mcp --scenario <your-scenario>
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```
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See the [README](./README.md) for full CLI options and the [SDK Integration Guide](./SDK_INTEGRATION.md) for testing against a real SDK.
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## Pull requests
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- Register your scenario in the right suite in `src/scenarios/index.ts`
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- Run against at least one real SDK before opening the PR — we'll ask what the output looked like
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- Keep PRs focused; one feature or scenario group at a time
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