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

With no annotations provided, the description carries the burden of behavioral disclosure. It discloses that the body is form-encoded and fixed, and that the operation is idempotent ('Calling it twice is the same as calling it once'). However, it doesn't mention side effects, error handling, or whether the operation is reversible, which is a gap for a mutation endpoint.

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 two sentences with no filler. The primary action and mechanism are front-loaded, followed by concise context about the header and idempotency. Every sentence contributes 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 simple tool with one parameter and no output schema, the description covers the essential aspects: what it does, when it's used, the fixed form-encoding, and idempotency. It lacks explicit error handling or response details, but those are not critical for a one-parameter unsubscribe endpoint. Overall, it's adequately complete.

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?

The schema documents the token as a 'Signed preference token' and the description refers to it as a 'signed capability,' which is essentially the same meaning. The description adds context about the token coming from the List-Unsubscribe-Post header, but it doesn't provide additional format or generation details beyond what the schema already conveys. Since schema coverage is 100%, the description adds marginal value.

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: 'Apply one-click unsubscribe through a signed capability.' It specifies the mechanism (signed capability) and the context (mail clients calling from the List-Unsubscribe-Post header), distinguishing it from other preference tools by focusing on the unsubscribe action. This is a specific and unambiguous purpose.

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 explains the primary use case: it is the endpoint mail clients call from the List-Unsubscribe-Post header, which tells an agent when to invoke it (automated unsubscribe from email clients). It doesn't explicitly mention when not to use it or compare to alternatives like commsharbor_preference_get, but the context is clear enough to infer appropriate usage.

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