set_primary_phone

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

With no annotations, the description carries the burden of behavioral disclosure. It adds an access requirement and a restart/session flow, which is useful operational behavior. However, it does not disclose side effects such as whether the previous primary phone is automatically demoted or whether the phone must be verified before this operation succeeds.

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 core action is front-loaded in a concise first sentence. The second sentence provides necessary access/authentication steps, though it is slightly verbose with the restart and sign-in alternatives. Overall, there is no wasted content.

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 operation, the required parameter source, and authentication requirements. It does not mention how to obtain a phone record ID or what the response is, but those are less critical given the clear schema and sibling tool list_phones.

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 already documents the only parameter, 'id', with 'Phone record ID to set as primary', covering 100% of parameters. The description adds no additional meaning beyond this, so the 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 states a specific verb ('Set'), a specific resource ('a phone number'), and the target state ('primary phone for the account'). This clearly distinguishes it from sibling tools like set_primary_email and set_primary_profile by naming the phone resource explicitly.

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?

There is no guidance on when to use this tool versus alternatives such as list_phones or set_primary_email. The only contextual note is the ACCESS prerequisite about needing a Proof account or starting a login session, which is operational setup rather than a usage-selection guideline.

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