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

Annotations already declare readOnly, idempotent, non-destructive, and non-open-world behavior, so the safety profile is covered. The description adds non-obvious payload information — that the response also carries the FTC click-to-cancel rule status and UK rules (uk_rules) — which the agent could not infer from the schema or 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?

Three front-loaded sentences with no fluff, and the extra-return disclosure is placed at the end where it belongs. The opening sentence duplicates the title verbatim, which is a small redundancy rather than a structural problem.

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?

There is no output schema, so the description usefully names what comes back (covered services plus FTC and UK rule status). Combined with the schema's full parameter documentation, an agent has enough to call it correctly; only the exact shape of the returned service list is unstated.

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%; the country and category parameters are fully documented in the schema, including the GB/UK exclusion behavior and the category list. The description adds nothing about filtering semantics beyond that, so the baseline of 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?

The description states a specific resource — the catalog of subscriptions the service can cancel — and the query intent it answers, which clearly separates it from siblings like get_cancel_steps and identify_charge. It never names those siblings explicitly, so differentiation is inferable rather than stated.

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?

Two concrete example phrasings ('which subscriptions can you help me cancel?', 'what gyms do you know?') give clear usage context. It stops short of any when-not-to-use guidance or explicit routing to the sibling tools for cancel steps, reminders, or charge identification.

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