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

Annotations already declare the mutation (readOnlyHint=false), the external side effect (openWorldHint=true) and non-idempotency, so the safety profile is covered. The description adds the account-state precondition, but says nothing about failure behavior on accounts with existing passwords, link expiry, or rate limits on repeated sends.

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?

A single front-loaded sentence with the precondition stated before the action and no filler. Every clause carries information the agent needs.

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 zero-parameter, no-output-schema tool the description is largely sufficient, but with no parameters it is unclear whether the email goes to the authenticated caller or another user, and no failure or idempotency-specific guidance is given beyond the annotations.

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 tool takes zero parameters, so there is nothing for the description to disambiguate at the parameter level; baseline applies. The one implicit question, whose account is targeted, is a scoping issue rather than a parameter issue.

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?

States a specific verb and resource: 'email the user a link to set a Caly password,' with the qualifying state ('account that signs in only with Google or Apple'). This is clearly distinct from change_password or request_email_verification, though it never names those siblings to make the contrast explicit.

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 precondition 'For an account that signs in only with Google or Apple' is an effective when-to-use signal and implicitly excludes accounts that already have a password. It stops short of naming alternatives (change_password) or stating what happens if the precondition isn't met.

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