Remember

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

With no annotations, the description carries the full burden and does so well: it discloses that only user-attributed content is kept, that newer statements supersede older ones about the same subject, that superseded entries remain in history, and that redundant restatement is a no-op. These deduplication and idempotency semantics are exactly the behavioral traits an agent cannot infer from the schema.

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

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

Purpose and content types are front-loaded, followed by parameter guidance and then behavioral rules, so structure matches reading order. It is a dense paragraph with no wasted clause, though splitting the deduplication rules into their own sentence group would aid scanning.

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

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

For a mutation-style tool with no annotations and no output schema, the description covers write semantics, attribution rules, conflict resolution, and idempotency. The remaining gap is what a successful call returns (confirmation, identifier, or nothing), which the agent may want to know for follow-up calls.

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

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

Schema coverage is 100%, so baseline is 3, but the description adds real meaning: it explains the text-vs-messages tradeoff and the filtering behavior of messages ('only what the user said or agreed to is kept'), plus the intent behind observed_at. It stops short of clarifying what happens when both text and messages are passed, which the schema also leaves open.

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

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

Opens with a specific verb and object: 'Keep something worth remembering about the user or their work,' then enumerates the acceptable content types (preference, fact, decision, correction). The write-side framing clearly separates it from recall/forget/history/diff siblings without relying on the name alone.

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

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

Gives concrete usage guidance: prefer the user's own words for text, use messages when you want role-filtering, and reserve observed_at for earlier/imported statements. It never explicitly excludes a sibling tool by name, but the write-vs-read boundary is unambiguous from context.

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