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

Annotations already declare readOnly, idempotent, non-destructive, so the safety profile is covered. The description still adds real context beyond that: it is free, results are newest-first, null means 'not yet', and it clarifies the subtle 'matched isn't agreed' rule plus what aired means. Only pagination/limits are left unstated.

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?

It is dense and front-loaded — cost and scope first, then field meanings, then the return shape. The middle sentence is a long run-on that packs many clauses, which slightly hurts scanability, but no sentence is filler.

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?

There is no output schema, and the description compensates by describing the return object ({ character_id, matches }) and the per-row shape, including the all-characters variant. For a zero-required-parameter read tool this leaves nothing an agent needs missing.

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 description coverage is 100%, so the baseline is 3. The description restates that omitting character_id returns all of yours and that each row includes character_id, but this essentially duplicates the schema's 'optional: none lists them all' rather than adding new semantics. agent_id is not mentioned at all.

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?

The description names the exact resource (YOUR characters' matches), states ordering (newest first), and enumerates the fields each row carries (who, when, both answers, agreement state, run_by, air date). Paired with the title and sibling set, an agent can tell this is the personal matches listing rather than my_dates or my_notifications without opening the schema.

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?

'Free. YOUR characters' matches' implies when it is appropriate and 'Once it's agreed, book it' hints at a follow-up action, but no sibling tool is named as an alternative and there are no explicit when-not conditions. Usage is implied rather than spelled out.

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