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

Annotations already cover safety (readOnly, idempotent, non-destructive, openWorld), so the lower bar applies. The description still discloses non-obvious payload content — that it also returns FTC click-to-cancel rule status and UK rules (uk_rules) — which is genuine behavioral information beyond the 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?

Two short sentences, front-loaded with the resource and followed by example triggers. Minor waste in the cryptic trailing "(uk_rules)" fragment, but nothing bloated.

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 read-only, zero-required-param listing tool with no output schema, the description conveys what the tool covers and what extra regulatory information comes back. Only the return shape of the subscription list itself is left implicit, a minor gap.

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%, so the country and category parameters are fully documented in the schema, including the country defaulting behavior. The description adds no syntax, format, or filtering detail beyond that, so the baseline 3 is appropriate.

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 the resource — the catalog of subscriptions Cancel My Sub covers — and identifies what the tool can answer. The verb is only implied ("returns"), and the title is largely repeated, but an agent can distinguish this listing tool from get_cancel_steps and identify_charge.

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?

It gives concrete example utterances ("which subscriptions can you help me cancel?", "what gyms do you know?") that map user intent to this tool, which is strong routing guidance. It does not name alternative tools or state when not to use it, 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.