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MCP Tools Reference

Lattice exposes five MCP tools to Claude Code. All tools are available when the MCP server is configured (see MCP Setup).

lattice_ingest

Save a fact or text chunk to memory.

Use for: a single fact, a decision, a preference, a short note.

lattice_ingest(
  text="decided to use PostgreSQL with UUID primary keys",
  source_id="claude-code",           # optional, defaults to "mcp"
  metadata={
    "source": "user",
    "observed_at": "2025-11-14T09:12:00Z"
  }
)

Returns: {atoms_new, atoms_updated, duplicates_skipped, atom_ids}

When Claude Code calls this: when you share a fact, decision, or preference during a conversation. Claude Code calls this immediately when you share something worth remembering.

lattice_capture

Save a session summary. Wraps lattice_ingest with source_id="claude-code" and treats the input as a conversation chunk.

Use for: end-of-session summaries. Call this when the user says "save", "done", "wrap up", or "end session".

lattice_capture(
  text="user: ...\nassistant: ...",   # conversation chunk
  metadata={
    "source_id": "claude-code",
    "observed_at": "2025-11-14T10:30:00Z"
  }
)

Returns: same as lattice_ingest

lattice_select

Find relevant atoms for a query. Returns raw atoms without synthesis — use when you want to inspect the evidence pack directly.

lattice_select(query="what did I decide about the database schema?")

Returns: list of atom dicts with id, kind, subject, content, observed_at, source_id, quality_score

Use for: when you want to ground an answer in retrieved atoms before composing a response yourself.

lattice_answer

Find relevant atoms + synthesize a prose answer. One stop for recall questions.

lattice_answer(question="what coffee do I like?")

Returns: {answer: str, atoms: list[dict], pii_protected: bool}

Use for: when the user asks a recall question ("what did I decide about X?", "what do I prefer?", "remind me of Y"). Claude Code should call lattice_answer and ground the response in the returned atoms.

lattice_status

Return atom count, streak, and today's activity.

lattice_status()

Returns:

{
  "atom_count": 147,
  "streak_days": 12,
  "today": {
    "captures": 3,
    "recalls": 2
  },
  "pii_active": false
}

Claude Code behavior guidelines

These are the rules Claude Code follows when Lattice MCP is configured:

  1. When the user shares a fact, preference, or decision → call lattice_ingest immediately. Do not wait.
  2. When the user asks a recall question → call lattice_answer first. Ground the response in returned atoms.
  3. When the user says "save", "done", "wrap up", or "end session" → call lattice_capture with a summary of decisions and conclusions from the session.
  4. Single fact from the user → set metadata.source="user", metadata.source_id="claude-code", metadata.observed_at=<current ISO timestamp>.
  5. Conversation chunk → format as "user: ...\nassistant: ..." and omit metadata.source — the pipeline attributes per-turn automatically.
  6. Do not save anything to ~/.claude/projects/.../memory/ — Lattice is the sole memory store.