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

Goes well beyond the annotations by disclosing behavioral detail: 'on' means at most one email a day and only while new entries arrive, the full set of return states (ready, unconfirmed, no_address, not_configured, owner_opted_out), and the one-time confirmation email flow. This is exactly the extra context an agent needs to set expectations.

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?

Front-loaded with the purpose sentence, then behavioral detail; the long parenthetical state list is information-dense but earns its place since there is no output schema. Slightly dense overall but no wasted sentences.

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 mutation tool with no output schema, the description fully covers what changes, what the response means, and the confirmation caveat. An agent can call and interpret it correctly without further inference.

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 the schema already documents digest (true/false), instance_id, and the optional passport_token. The description adds no syntax or format detail beyond that, so 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?

States a specific verb+resource+scope: 'Turn your form inbox's daily digest email to your owner on or off.' It is clearly distinguishable from nearby siblings like form_submissions or delete_form_submissions, which concern submissions rather than the digest-email setting.

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 explains the effect of each state but gives no explicit when-to-use-vs-alternative guidance or prerequisites beyond the schema. Usage (flip the digest on/off) is only implied by the purpose statement, with no named alternative tool.

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