Look up a user's attribution

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

Beyond annotations, the description discloses the resolution rule (newest install only), the meaning of a 404 customer_user_not_found, the authorization requirement ('Read scope is enough'), and what each attribution_status value means. That is substantive behavioral context not available in the structured fields.

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?

Front-loaded verb and scope in one dense sentence, followed by a short error-semantics sentence; almost every clause carries information. The enumerated field/status list makes the opening sentence long but it is still readable.

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 no output schema, the description carries the burden of describing the return payload, which it does by naming the fields and status values, and it covers the error case and permission requirement. Nothing an agent needs in order to call it correctly is 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%, including the refusal rule for email/phone-like ids. The description mostly restates the schema's customer_user_id mapping and says nothing about app_id, so the baseline 3 applies.

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 ('look up the attribution of one of your users') and enumerates exactly what is returned (campaign, ad set, ad, network, match confidence, attribution_status). This clearly distinguishes it from aggregate siblings such as get_attribution_rollup.

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?

Explains the required lookup key (the customer_user_id passed to AttriKit.setUserID) and that the result is the user's newest install, plus the 404 condition and required read scope. It does not explicitly name a sibling alternative, so it stops short of a 5.

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