> ## Documentation Index > Fetch the complete documentation index at: https://docs.aethis.ai/llms.txt > Use this file to discover all available pages before exploring further. # MCP server overview > Install and configure aethis-mcp for Claude Code, Claude Desktop, Cursor, and Windsurf. ## What it is MCP (Model Context Protocol) is an open standard that lets AI coding agents call external tools directly from a conversation — no shell, no files. `aethis-mcp` implements this protocol, exposing 27 tools for evaluating eligibility and authoring rules from legislation. Install it once. After that, your coding agent can call `aethis_decide`, `aethis_create_ruleset`, `aethis_generate_and_test`, and `aethis_publish` as naturally as it calls any other tool. **Decision tools** (evaluate, schema, explain) work with no API key.\ **Authoring tools** (create, generate, publish) require an API key. *** ## Quick install (recommended) If you have [`aethis-cli`](/interfaces/cli) installed, one command wires up the MCP server in your editor's config — picks up the API key cached by `aethis login`, drops a canonical `aethis` server entry into the right config file for each target, and preserves any other MCP servers you already have. ```bash theme={null} # All four clients at once: aethis mcp install --target all # Or one at a time: aethis mcp install --target claude-code # writes ./.mcp.json (project-local) aethis mcp install --target cursor # ~/.cursor/mcp.json aethis mcp install --target claude-desktop # ~/Library/Application Support/Claude/... aethis mcp install --target windsurf # ~/.codeium/windsurf/mcp_config.json ``` Restart your editor to pick up the change. Re-run after `aethis account generate` rotates your key — the entry updates in place. Reverse with `aethis mcp uninstall --target ` (only removes the `aethis` entry). Don't have `aethis-cli`? Use the manual install below. *** ## Manual install (without aethis-cli) ```bash theme={null} # Decision tools only (no key needed) claude mcp add aethis -- npx -y aethis-mcp # With authoring access claude mcp add aethis -e AETHIS_API_KEY=ak_live_... -- npx -y aethis-mcp ``` Add to `~/Library/Application Support/Claude/claude_desktop_config.json` (macOS) or `%APPDATA%\Claude\claude_desktop_config.json` (Windows): ```json theme={null} { "mcpServers": { "aethis": { "command": "npx", "args": ["-y", "aethis-mcp"], "env": { "AETHIS_API_KEY": "ak_live_..." } } } } ``` Omit the `env` block if you only need decision tools. Add to `.cursor/mcp.json` or `.windsurf/mcp.json` — same JSON structure as Claude Desktop above. The API key must be set in the MCP client's config file, not in your shell profile. The MCP server process doesn't inherit shell environment variables. *** ## Prompts MCP prompts are pre-built workflow guides that compatible clients can surface as selectable templates. | Prompt | Description | | --------------- | ----------------------------------------------------------------------------------------------- | | `aethis-author` | Step-by-step TDD workflow: gather requirements → create ruleset → generate → refine → publish | | `aethis-decide` | Decision workflow: find ruleset → get schema → evaluate. Accepts optional `ruleset_id` argument | *** ## Try it — no API key required Decision tools work immediately. Two examples you can try now: **UK Free School Meals — child eligibility:** > Is a 10-year-old at a state-funded school eligible for Free School Meals? ``` aethis_decide({ ruleset_id: "aethis/uk-fsm/child-eligibility", field_values: { "child.age": 10, "child.school_type": "state_funded" }, include_trace: true }) ``` ```json theme={null} { "decision": "eligible", "fields_provided": 2, "fields_evaluated": 2, "trace": { "age_check": "PASS — age 10 is within 4–15 (FSM Regulations 2014, Regulation 3(1))", "school_type_check": "PASS — school_type is state_funded (FSM Regulations 2014, Regulation 3(2)(b))" } } ``` **Spacecraft crew certification — Vogon applicant:** > Is a Vogon eligible for spacecraft crew certification? ``` aethis_decide({ ruleset_id: "aethis/spacecraft-crew-certification", field_values: { "space.crew.species": "Vogon" }, include_trace: true }) ``` ```json theme={null} { "decision": "not_eligible", "fields_provided": 1, "fields_evaluated": 11, "trace": { "species_check": "FAIL — species is 'Vogon' (disqualifying, Section 3)" } } ``` One field provided. The engine determined a Vogon was disqualified without asking about flight hours, medical certificates, or anything else. It found the shortest path to a decision from the facts it already had. *** ## Authoring with a coding agent Paste a policy document into Claude Code, Cursor, or Windsurf and ask the agent to author rules. The agent runs the tool calls; you confirm section boundaries, field names, test cases, and domain corrections at checkpoints. Full procedural flow: [Author a rule from legislation](/recipes/author-a-rule). ```text theme={null} Use Aethis MCP to turn this policy into a tested ruleset. Draft the input fields and test cases first, then stop for my approval. Do not publish until all tests pass. ``` For the human-facing workflow, see [AI coding agent onboarding](/agents/onboarding). *** ## Authoring access Authoring is invite-only private beta — [request access](https://aethis.ai/developer-access). Generation tools call an Anthropic model on your behalf and accept the key per request; it is used only for that request and never stored. Prefer passing the key **by reference** — `anthropic_key_env` (the name of an env var that holds the key) or `anthropic_key_keychain` (a macOS keychain item) — rather than the deprecated raw `anthropic_key`, which lands verbatim in the host's session transcript. *** ## Troubleshooting | Error | Cause | Fix | | ---------------------------------- | ------------------------------------------------------------------ | ----------------------------------------------------------------------------------------------------------------------------------------------- | | `"API key is required"` | `AETHIS_API_KEY` not set | Set in MCP client config (not shell profile). Decision tools don't need a key. | | `"Ruleset not found"` (404) | Wrong ID or archived ruleset | For public showcase rulesets, use `aethis_discover_rulesets`; for private tenant rulesets, use `aethis_list_projects` → `aethis_list_rulesets`. | | `"Cannot publish: tests failing"` | Tests don't pass | Fix with `aethis_refine`, or pass `force: true` to override (not recommended for production). | | Rate limit exceeded (429) | Daily limit hit | Wait and retry. Contact [eng@aethis.ai](mailto:eng@aethis.ai) for a higher tier. | | Generation timeout (504) | Client timed out — normal for complex rules (5–15 min server-side) | See [Handling generation timeouts](/authoring/rule-generation#handling-generation-timeouts). | | Date field named in `field_errors` | Value is neither ISO `"YYYY-MM-DD"` nor an integer ordinal | Pass either form (ISO accepted since engine 0.31.0; rulebooks need ordinals) — see [Date field values](/reference/errors#date-field-values). | **Help improve this page** If something here is unclear or missing an example, use the feedback button at the bottom of the page. Found a bug? [Open a GitHub issue](https://github.com/Aethis-ai/feedback/issues). Evaluating Aethis for a regulated workflow? [Contact us directly](https://aethis.ai/developer-access).