anc.dev

anc.dev exposes the agent-native CLI standard catalog over a streamable HTTP MCP server, per spec revision 2026-07-28. Every scored CLI, every principle of the spec, and the vendored spec sections are queryable without authentication. Response format is driven by the Accept header. The server accepts application/json alone, text/event-stream alone, both together (any order, any q-values), */*, and absent Accept. JSON wins ties; q-values resolve unequal preferences. A request that accepts neither MIME type receives 406 Not Acceptable with a text/plain body, no JSON-RPC envelope, since the rejection is pre-JSON-RPC. Surface: 13 tools (list_tools, get_tool, search_tools, list_principles, get_principle, list_spec_sections, get_spec_section, get_scorecard, score_cli, get_website_audit, audit_website, list_website_audits, get_web_remediation) plus 5 resources total (1 concrete anc://registry plus 4 templates anc://tool/{slug}, anc://principle/{n}, anc://spec/{section}, anc://scorecard/{binary}). Per-item records live behind the templates; full schemas are on tools/list and resources/templates/list. The four web tools score a website and its MCP server against the same eight principles as a CLI. get_website_audit reads a cached web scorecard by URL (miss returns next_tool: audit_website); audit_website runs a fresh audit and returns a single terminal scorecard with no progress notifications (stateless mode); list_website_audits returns the curated web leaderboard; get_web_remediation returns the static fix for a web-audit check id. Web scorecards carry the score_pct/score/categories/results shape at https://anc.dev/web-scorecard-schema. Every read and transact tool returns the one result envelope: { kind, tier, target, scorecard_url, markdown_url, json_url, freshness, spec_version, scorecard } plus the lane metadata. The same envelope is what https://anc.dev/score/<target>/json serves, so a tool result and the page an agent follows it to cannot disagree. Follow scorecard_url for the page, markdown_url or json_url for the pinned twins. Errors carry on two layers. Tool-level failures return CallToolResult with isError: true plus a textual message; the JSON-RPC envelope itself is successful. Transport-level failures return JSON-RPC error envelopes at HTTP 200 (-32099 rate-limit breach at either limiter, -32022 with data.supported listing 2026-07-28 when the disabled legacy lane rejects a request) or at HTTP 400 (-32700 malformed JSON with id null, -32600 invalid batch, -32020 header mismatch, and -32022 with data.requested for an unsupported version claim). The 406 Accept-header rejection is the one transport error that bypasses the JSON-RPC envelope. Rate limits are split. 60 requests per 60 seconds per IP gate every call (MCP_LIMITER). 5 fresh audits per 60 minutes per IP gate score_cli cache-miss audits only (MCP_AUDIT_LIMITER). audit_website has its own budget: a per-IP burst limiter (WEB_AUDIT_LIMITER_IP) plus 30 fresh audits per 60 minutes per IP, no anon fallback. All keyed on cf-connecting-ip; the read tier falls back to a shared anon bucket, the audit tiers reject on missing IP rather than consuming a shared bucket. Four of the five kill switches let the operator disable the whole surface (MCP_ENABLED), only the cost-bearing CLI audit tool (MCP_LIVE_SCORING_ENABLED), the website audit (WEB_AUDIT_ENABLED), or only the following of declared hosts (WEB_AUDIT_FOLLOW_ENABLED) without a deploy; the fifth (MCP_LEGACY_ENABLED) surfaces as the -32022 legacy reject above. By default (follow_declarations true) a website audit also contacts third-party hosts the site declares. An MCP server the site's server card names gets GETs for the documents that could confirm it (a card at <endpoint>/server-card, its host's /.well-known/ai-catalog.json, RFC 9728 protected-resource metadata) and is wire-probed (JSON-RPC POSTs, a CORS preflight) only after one of those documents on the endpoint's own host names the endpoint. An API host anchored in the site's api-catalog gets document fetches (its OpenAPI description) and one GET to a nonsense path on the site's declaration alone. anc sends no plaintext request: an http URL, declared or linked, and any redirect to http, is never requested. Each audit follows at most 4 off-origin hosts with at most 12 follow-phase document requests inside a 6-second follow window, so following lengthens an audit's wall time. Across all audits and sites, following is also capped at about 30 audits per hour per declared registrable domain; an audit past that cap leaves that domain's hosts unprobed, and when the site has a saved scorecard from the last 24 hours that audit is returned without replacing it, with no scorecard_url, markdown_url, or json_url. follow_declarations false audits only the site and returns a result that is never saved, and the operator can switch following off for every audit (WEB_AUDIT_FOLLOW_ENABLED). Spec revision is pinned to 2026-07-28; the /.well-known/mcp/server-card.json server card advertises the same value, and the two are bumped in lockstep when the SDK is upgraded. Connect now at https://anc.dev/mcp (no authentication). Full recipes remain at https://anc.dev/mcp-skill.md.