# ColdState

> Deterministic Knowledge Infrastructure for AI agents. A 48M-entry, 35-domain knowledge base and zero-knowledge custom indexes, queried over a REST API or the Model Context Protocol. Same query + same kb_snapshot ⇒ byte-identical results; every result carries a stable id and a content_hash so facts can be cited and re-verified. No embeddings, no vector database, no per-query inference.

ColdState is built for agents to use directly: fetch a fact, cite it, verify later that it has not changed. The MCP endpoint is https://cold-api.coldstate.ai/mcp (Streamable HTTP, stateless). Authentication is a bearer API key obtained at https://services.coldstate.ai/signup.

## Connect

- [MCP endpoint](https://cold-api.coldstate.ai/mcp): POST, Streamable HTTP. Header: Authorization: Bearer <COLDSTATE_API_KEY>
- [MCP server manifest](https://cold-api.coldstate.ai/.well-known/mcp/server.json): official registry server.json
- [OpenAPI 3.1](https://cold-api.coldstate.ai/openapi.json): full REST description of the public API
- [Sign up / API keys](https://services.coldstate.ai/signup): free tier available

## Documentation

- [API reference](https://services.coldstate.ai/docs): every endpoint, auth, errors and limits
- [Quickstart](https://services.coldstate.ai/docs/quickstart): API key, first search, custom indexes, with curl examples
- [MCP server](https://services.coldstate.ai/docs/mcp): endpoint, client setup and all tools with their arguments
- [Fetch, cite, verify](https://services.coldstate.ai/docs/fetch-cite-verify): reproducible citations with stable ids, content hashes and snapshots
- [Why deterministic](https://services.coldstate.ai/why-deterministic): the guarantees and what they cost
- [What is Deterministic Knowledge Infrastructure](https://services.coldstate.ai/deterministic-knowledge-infrastructure): category definition and comparison with RAG and knowledge graphs
- [Pricing](https://services.coldstate.ai/pricing): Free, Starter, Growth, Pro, Enterprise

## MCP tools

- [coldstate_search_global](https://services.coldstate.ai/docs/mcp#coldstate_search_global): Search the 48M-entry global knowledge base (35 domains); deterministic ranking, Ψ score + state per result
- [coldstate_fetch](https://services.coldstate.ai/docs/mcp#coldstate_fetch): Fetch a knowledge entry verbatim by stable id, with content_hash and kb_snapshot
- [coldstate_cite](https://services.coldstate.ai/docs/mcp#coldstate_cite): Canonical, reproducible citation for an entry (id + content_hash + kb_snapshot)
- [coldstate_verify](https://services.coldstate.ai/docs/mcp#coldstate_verify): Verify a previously cited fact is unchanged by comparing its content_hash
- [coldstate_snapshot](https://services.coldstate.ai/docs/mcp#coldstate_snapshot): Current knowledge-base snapshot id for pinning reproducible results
- [coldstate_related](https://services.coldstate.ai/docs/mcp#coldstate_related): Deterministically related entries via the concept-cluster graph
- [coldstate_resolve](https://services.coldstate.ai/docs/mcp#coldstate_resolve): Resolve a name/alias/surface form to a canonical entry id
- [coldstate_batch_search](https://services.coldstate.ai/docs/mcp#coldstate_batch_search): Several queries against one consistent snapshot in a single call
- [coldstate_isomorph](https://services.coldstate.ai/docs/mcp#coldstate_isomorph): Cross-domain structural analog of an entry (same structure, different domain)
- [coldstate_stats](https://services.coldstate.ai/docs/mcp#coldstate_stats): Query coverage / state distribution, or global KB stats
- [coldstate_domains](https://services.coldstate.ai/docs/mcp#coldstate_domains): List knowledge domains with entry counts
- [coldstate_capabilities](https://services.coldstate.ai/docs/mcp#coldstate_capabilities): Machine-readable manifest: tools, domains, snapshot, guarantees, limits
- [coldstate_search](https://services.coldstate.ai/docs/mcp#coldstate_search): Search one of your own zero-knowledge custom indexes
- [coldstate_list_indexes](https://services.coldstate.ai/docs/mcp#coldstate_list_indexes): List your custom indexes
- [coldstate_browse_documents](https://services.coldstate.ai/docs/mcp#coldstate_browse_documents): Browse a custom index (ref_ids + metrics; no stored text)
- [coldstate_explain](https://services.coldstate.ai/docs/mcp#coldstate_explain): Explain why a document ranked for a query, term by term

## Guarantees

- Deterministic: identical query + kb_snapshot ⇒ identical results, stable ordering with id tiebreak.
- Verifiable: every entry has a stable id and a sha256 content_hash; coldstate_verify confirms a citation is unchanged.
- Zero-knowledge custom indexes: your document text is never stored, only a derived index keyed by your own reference ids.
- Limits: 2000 chars per query, 10 queries per batch, 100 results per query.

## Optional

- [Privacy](https://services.coldstate.ai/privacy)
- [Terms](https://services.coldstate.ai/terms)
- [Health](https://cold-api.coldstate.ai/health)