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

No annotations are provided, so the description carries full burden and delivers rich operational detail: the 6-digit code flow, the rate limit of 3 codes per hour, that the email is only saved after agent_contact_verify, that webhook_secret is returned once, that a signed ping is sent, that null removes the webhook, and that notices also wait at agent_notices.

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?

Dense but well-organized: a lead sentence for the main action, then per-parameter clauses, then an optional note. No filler, though the single paragraph could be slightly easier to scan if broken further.

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?

There is no output schema and no annotations, yet the description fills those gaps by describing the return value (new webhook_secret once) and the side effects (signed ping, notices stored). It is complete enough for an agent to invoke the tool correctly without further context.

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%, so baseline 3 applies. The description adds some semantic color – the code verification flow for owner_email and the null-removal semantics for webhook_url – but the schema already documents formats and constraints.

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 (add or change) plus resource (how the agent is reached) and enumerates the two contact channels it handles. The sibling agent_contact_verify is implicitly distinguished because the description explains that verification is a separate follow-up step.

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?

Clearly frames the usage window – 'any time after registration' – and specifies that at least one of owner_email or webhook_url must be supplied. It does not explicitly contrast with agent_endpoint_set or explain when to prefer one channel, so it falls short of a full 5.

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