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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so safety is covered. The description adds genuine value by disclosing the response payload contents — including USD price and checkout_url — which is important behavior an agent cannot infer from annotations.

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 verb and resource, with the payload list following. Every item roughly earns its place given no output schema, though 'verified network facts' is vague enough to be near-filler.

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 one parameter, full schema coverage, rich annotations, and no output schema, the description covers purpose, id provenance, and returned fields — enough to call it correctly. Only minor gaps remain, such as error behavior for an unknown id.

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 id property already says 'Plan id returned by search_plans', so the description's '(from search_plans)' merely restates it. No added syntax, format, or edge-case 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+scope: 'Full details of one plan by id'. It also names the sibling (search_plans) as the source of the id, so the agent can distinguish this point-lookup from the sibling search tool without opening either 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?

The parenthetical '(from search_plans)' makes the intended workflow clear: search first, then fetch details. It does not spell out when not to use this tool (e.g. when list-level data suffices), so it falls short of full explicit when/when-not guidance.

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