Create a collection

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

Adds real behavior beyond the annotations: an existing active collection succeeds with no change, a deleting/deleted one returns 409, and the operation is free (no billing impact). The idempotency point partly overlaps idempotentHint and destructiveHint=false is not elaborated (what is destroyed on a 409 path), but the error semantics and cost disclosure are genuine value-adds.

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?

Three compact sentences, front-loaded with the definition, then the idempotency/error behavior, then the optionality note and cost. Nothing is repeated and the 'Free.' fragment still carries actionable information.

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 one-parameter create tool with annotations covering readOnly/destructive/idempotent hints, the description covers purpose, optionality, error behavior, and alternatives. The only gap is what a successful response contains, which is a minor omission 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% and the single parameter is fully documented in the schema, including naming constraints. The description's 'for example one per event' echoes the schema's own example, so it adds little new meaning; baseline 3 applies when the schema already does the work.

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 ('Create a face collection'), gives a concrete use case ('for example one per event'), and implicitly distinguishes itself from restore_collection and recreate_collection by naming them as the alternatives in the conflict path. An agent can tell what this tool produces 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?

Goes well beyond a plain when-to-use: it says the call is optional because indexing into a missing collection also creates it, and it names restore_collection and recreate_collection for the 409/deleted case. Both the 'you may not need this' and 'here is the alternative when it fails' conditions are explicit.

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