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fact

Records an entity's scalar attribute, state, or preference as a subject, key, and value slot without LLM extraction; newer writes supersede prior values while preserving history.

Instructions

Record a scalar fact — an attribute, state, or preference — about an entity as a (subject, stateKey, value) slot, bypassing LLM extraction. The fact-shaped counterpart to relate: relate records edges between entities, fact records a single entity's slots (e.g. state.task.status=pending). A later write to the same stateKey supersedes the prior value (kept as history). Read them back via get(entities/{uid}) for the current slots, or get(facts/{uid}) for one.

Input Schema

Name	Required	Description
`scope`	No	Scope to write into — pick by who should see it. Defaults to personal (private to the user, syncs to their devices). Use "project" for facts tied to the current repo/codebase (shared with anyone who has repo access). Use "team" for the shared team brain (requires admitted membership, else E_PERMISSION).
`value`	Yes	The scalar value the slot holds, e.g. "pending", "Steven".
`source`	No	Provenance label for the appended event, e.g. "cli:fact". Optional; defaults to "mcp:fact".
`subject`	Yes	Subject entity the fact is about: entities/{uid}, a bare ULID, the literal "self", or a human display name (resolved case-insensitively, like maz get).
`stateKey`	Yes	Hierarchical slot address: lowercase, dot-separated, e.g. state.task.status, preference.coffee.milk. The first segment is the category (event\|state\|relationship\|preference\|plan\|absence\|timeless).
`eventStart`	No	When the fact became true in the world (RFC 3339 UTC). Optional; defaults to now.
`sourcePriority`	No	Recall-lane priority, 0..1. Optional; defaults to 1.0.

Output Schema

Name	Required	Description	Default
`name`	Yes	AIP resource name of the asserted Fact; pass to get(facts/{uid}).
`status`	Yes	Always "asserted" on success.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Oct 31, 2026

TDQS

A4.2/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations are empty, so the description carries the full burden, and it delivers the key non-obvious behavior: a later write to the same stateKey supersedes the prior value, which is retained as history. It also discloses that this bypasses LLM extraction. It does not cover failure modes or permission behavior beyond what the scope parameter already documents.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the action and slot shape, then sibling differentiation, a concrete example, supersede semantics, and read paths in that order. Every sentence carries information; nothing is restated from the schema verbatim.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 7-parameter mutation tool with an output schema (so return values need not be explained), it covers the slot model, supersede/history behavior, and how to read back. Gaps are the absence of guidance on removal (retractFact) and on error/permission outcomes.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the baseline is 3. The description reinforces stateKey as a hierarchical slot and combines it with a sample value, but adds no format or default detail beyond what the schema already documents for scope, source, eventStart, and sourcePriority.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Record a scalar fact ... as a (subject, stateKey, value) slot') and explicitly contrasts itself with the sibling `relate`: edges between entities vs. a single entity's slots. The parenthetical example (state.task.status=pending) makes the shape unambiguous.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives an explicit selection rule against `relate` and names the read path (get(entities/{uid}) for current slots, get(facts/{uid}) for a single fact). It does not mention `remember` (extraction-based writing) or `retractFact` for removal, so the when-not / deletion story is incomplete.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.