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

The description discloses a key behavioral trait: setting status to unsubscribed immediately excludes the contact from future campaigns. This adds value beyond the annotations, which only indicate idempotentHint and non-destructive. It does not contradict 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?

The description is two sentences, front-loaded with the main purpose, and includes a critical behavioral note. No wasted words.

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?

Given the tool has 9 parameters, 100% schema coverage, and no output schema, the description is sufficient. It explains the main action and a key side effect. It could mention that it replaces tags (as per schema) but that is already in the schema. Overall, complete enough.

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 has 100% description coverage for all parameters, so the description does not need to add much. It mentions 'including changing subscription status' which highlights the status parameter, but the schema already describes each parameter. 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 clearly states the tool updates an existing contact by email address and can change subscription status. It distinguishes from create_contact and list_contacts by specifying 'existing contact' and the update action.

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 implies usage for updating contact details and subscription status, but does not explicitly mention when not to use it or alternatives. However, the context of updating an existing contact is clear, and the sibling tools like create_contact provide contrast.

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