Get customer

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

Annotations already cover readOnlyHint, idempotentHint, destructiveHint and openWorldHint, so the safety bar is met. The description adds genuine domain context beyond that: it enumerates the returned data and explains the semantics of gives_access ("whether each one grants access now"), which an agent cannot get from annotations. It stops short of describing not-found behavior or error cases.

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?

A single sentence, front-loaded with the action and key, then the returned payload. No filler and every clause carries 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?

With no output schema, the description correctly shoulders the burden of describing return values and does so with four enumerated categories plus an interpretation hint for gives_access. Remaining gaps such as error/not-found behavior or whether results are cached are minor for a read-only lookup.

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%, so both parameters are already documented in the schema, dictating a baseline of 3. The description restates the customer_id key ("app user id") but says nothing about project_id, so it adds no meaning 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+resource ("Looks up a customer") and specifies the key (app user id) plus the payload returned: entitlements, attributes, subscriptions, one-time purchases. The singular lookup is clearly distinct from the sibling list-customers in spirit, but no sibling is named to make the boundary explicit.

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?

"Looks up a customer by app user id" implies the lookup key but gives no when-to-use guidance, no prerequisites, and no alternatives (e.g. list-customers for discovery vs. this for a known id). An agent must infer the selection rule.

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