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

With no annotations, the description carries the behavioral burden and does so for the key traits: it is 'free' and 'unauthenticated,' and returns sample rather than live data. It does not mention rate limits, pagination, or error behavior, but for a zero-param read-only sample tool the cost/auth/no-write disclosure is the substantive part.

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?

Two tight sentences, front-loaded with the free/sample framing. Slight redundancy in restating the check_carrier_identity purchase rationale already implied by naming the sibling, but no meaningful waste.

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 simple no-param sample tool with no annotations and no output schema, the description covers cost, auth, and which response shapes are demonstrated. It could be more complete by listing the fields present in the sample, but the essentials an agent needs to call it are present.

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?

Zero parameters, so the schema is trivial and fully self-documenting (100% coverage). There is nothing for the description to add on parameters, making the baseline of 4 appropriate.

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+resource (get identity sample) and explicitly frames it against two named siblings: it covers both screen_carrier_identity's free IdentityScreen shape and check_carrier_identity's paid IdentityAssessment shape. An agent can tell what this returns and how it relates to the identity-checking siblings without opening any 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?

Gives a clear usage context and the deciding condition: use it to see the paid response shape and evaluate data quality 'before spending USDC on check_carrier_identity.' It names the relevant alternatives, though it doesn't explicitly say when NOT to use it (e.g., vs. the generic get_sample sibling).

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