Search by a stored face

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

Adds important behavior beyond annotations: cost of 62 credits, return shape [{photo_id, score}], accepted point_id forms, and the point_not_found error for face point ids. Annotations already cover idempotency, openness, and non-destructiveness; the description adds the operational details an agent needs.

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 compact sentences, front-loaded with the core purpose, then the cost comparison, ID constraints, return format, and price. Every sentence carries useful information and there is no 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?

For a five-parameter search tool with full schema coverage and annotations, the description covers the essential gaps: cost, return format, accepted ID types, and the specific error case. No output schema exists, but the return shape is stated, so an agent has enough to call and interpret the result.

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 the schema documents all parameters. The description still adds meaning for point_id by specifying it must come from register_selfie for this collection and by explaining the UUID/unsigned-integer forms and the failure mode for face point ids. It does not add further meaning for limit or threshold, but those are already documented in 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 resource: find a registered person's photos using a stored point_id. It clearly distinguishes this from search_faces by being cheaper and from index_photo by rejecting face point ids. An agent can identify the exact operation 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?

Explicitly says when to use it: when you have the point_id returned by register_selfie and want to avoid resending the selfie. It also says when not to use it: face point ids from index_photo return reason=point_not_found. The alternative search_faces is named with a cost comparison.

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