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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is fully covered without the description. The description adds only the REST endpoint mapping, saying nothing about what a not-found token returns or any auth/rate-limit expectations.

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 short fragments with zero filler and the key constraint (single plan, by token) front-loaded. It is efficient, though terse enough that it reads more like a signature than a definition.

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 read tool with rich annotations this is close to sufficient, but there is no output schema, so the description could have said what a plan object contains; that omission leaves the agent without any expectation of the return payload.

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% and the plan_token property already carries the plan_... example, so the description's '(plan_...)' restates schema content rather than adding meaning. Baseline 3 applies when the schema does the heavy lifting.

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 the specific resource (plan), cardinality (one) and lookup key (token), plus the underlying endpoint GET /plans/{token}. That distinguishes it clearly from the sibling pinpayments_list_plans, though it never names the sibling explicitly.

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?

'One plan by token' implies the retrieve-by-identifier use case, but there is no explicit when-to-use guidance, no statement that pinpayments_list_plans should be used to discover tokens, and no mention of error behavior for an unknown token.

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