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

Annotations declare a non-destructive write, and the description adds real behavioral context beyond them: a failed list match writes nothing and returns candidates for disambiguation, `create_if_missing` creates a private list, and the returned details status must be reported exactly. It doesn't cover return shape or pagination, but the failure-mode disclosure is valuable.

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?

Four short sentences, front-loaded with what the tool does, then the list-resolution rules, then the reporting obligation. No filler and no repetition of schema text.

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?

With seven optional parameters, no output schema, and only hints about what is returned ('candidates', 'details status'), the description covers the ambiguous cases an agent is most likely to hit. It leaves the actual return payload underspecified, which matters somewhat given there is no output schema.

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; the description still adds intent-level nuance by framing Inbox as a deliberate omission and by scoping `create_if_missing` to cases where the person explicitly wants a new list. It does not add syntax or matching detail beyond the schema.

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?

States a specific verb and scope: 'Capture one pick with the person's own note.' The singular 'one pick' implicitly contrasts with the batch sibling add_items, but it never names that sibling or add_saved_item, so an agent must infer the routing.

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 explicit conditional guidance: omit `list` only to deliberately use Inbox; on an ambiguous or missing list nothing is written and candidates are returned, so ask the person or set `create_if_missing`. It stops short of naming alternative tools (e.g. add_items for multiple picks) but covers the in-tool decision points well.

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