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

Annotations declare a non-read-only, non-destructive, non-idempotent mutation, and the description adds the key behavioral constraint: consent evidence must accompany the call. It does not say what happens if the address is not currently unsubscribed, or what the response contains, but the consent-proof requirement is substantive context 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?

Three short sentences, front-loaded with the action, then the condition, then the hard prohibition. Every sentence carries a distinct instruction and none is redundant.

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 three-parameter mutation with a nested consent object and no output schema, the description covers the critical decision logic and the shape of the required evidence. It leaves minor gaps around failure modes and the meaning of project_id, but an agent could call this correctly from what is given.

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 0% for the top-level parameters, so the description must compensate. It does so by explaining that the consent object should carry 'what they agreed to, from where and when,' which maps onto wording, ip_address, user_agent, and consented_at. project_id and email remain unexplained, keeping it below a 5.

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 verb and resource: 'Opt an unsubscribed address back in to marketing email.' That is clearly distinct from unsubscribe_email and block_email. It stops short of naming the nearest sibling (record_consent) or explicitly contrasting with it, so it is clear but not fully differentiated.

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 an explicit precondition ('Only do this when the person asked to') and an explicit prohibition ('Never resubscribe someone on the user's say-so alone'). The agent knows both when to call it and when to refuse, which is exactly the guidance a mutation tool needs.

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