set_primary_email

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

No annotations are provided, so the description carries the burden of disclosing behavior. It does explain the access/auth requirement and the need to retry after creating a session, which is useful. However, it does not disclose side effects such as what happens to the previous primary email, whether verification is required, or what the success/failure response looks like.

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 compact and front-loaded with the core purpose, followed by a clearly marked access note. Every sentence adds necessary information, and there is no redundancy with the schema or the tool name.

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 one-parameter mutation with no output schema, the description covers the main action and the critical auth precondition. It could be slightly more complete by pointing to list_emails for retrieving the email record ID or mentioning whether the email must already be verified, but these are not fatal omissions.

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 100%, and the single parameter 'id' is already described as the 'Email record ID to set as primary'. The tool description adds no additional parameter meaning beyond what the schema provides, so the baseline score of 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 action ('Set'), the resource ('an email address'), and the scope ('as the primary email for the account'). This distinguishes it from related email tools like list_emails, remove_email, and start_add_email, as well as the sibling set_primary_phone.

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 gives explicit preconditions: a Proof account is required, and it explains how to authenticate by either setting PROOF_API_KEY or using start_login. It does not explicitly name alternatives or exclusion conditions, but the access guidance is clear enough for an agent to know when it is ready to call this tool.

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