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

The description explicitly states 'MODIFIES live data' and 'stops all future charges', adding behavioral context beyond the destructiveHint annotation. It also mentions the required cancellation_reason, but does not cover reversibility or authorization requirements.

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?

The description is extremely concise: two sentences covering purpose and side effects, plus a third for the REST endpoint and return value. No filler or redundant 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?

For a cancellation tool with no output schema, the description covers the action, side effects, required parameter, and return shape ('Returns { subscription }'). It is reasonably complete, though lacks details on response fields and error states.

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 baseline is 3. The description restates that cancellation_reason is required and mentions optional comments, but does not add new meaning or constraints beyond what the schema provides.

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 clearly states the tool cancels an active subscription and stops future charges. The verb 'CANCEL' is strong and specific to the resource 'subscription'. It distinguishes itself from sibling tools like recharge_activate_subscription and recharge_skip_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?

The description clearly indicates the tool is for canceling active subscriptions, but does not explicitly state when NOT to use it or provide direct alternatives (e.g., skipping a charge instead). The context is present but excludes negative guidance.

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