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

Annotations already indicate non-destructive (destructiveHint=false) and idempotent (idempotentHint=true). Description adds that the row is deactivated not deleted, preserving history – a valuable behavioral detail beyond 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 sentences, no redundant words. Action verb first, followed by two important behavioral details. Efficient and easy to parse.

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 1-parameter tool with no output schema, the description covers purpose, constraints (ownership), effect (deactivate vs delete), and side-effect (history preserved). Could mention idempotency explicitly but annotation covers it.

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% with a clear schema description. The description adds context that the id is the one 'returned by subscribe', linking it to another tool and clarifying its origin.

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 action ('Cancel a subscription by id') and distinguishes itself from siblings like subscribe (creates) and list_subscriptions (lists) by specifying resource and scope.

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?

Clearly indicates when to use: cancel own subscription. Implicitly tells when not to: ownership is enforced, so only own subscriptions. Does not explicitly name alternative tools but context from siblings is sufficient.

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