voidmail_sending_limits

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

Annotations already declare readOnlyHint/idempotentHint/destructiveHint=false, but the description adds non-obvious context beyond them: the call does not consume quota or reserve capacity, and the Retry-After signal implies rate-limited responses an agent must honor. What is missing is any hint about what the limits payload contains, though no output schema exists to cover that gap.

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?

Three short sentences, front-loaded with the action and its scope, followed by the two constraints an agent actually needs. No filler or restatement of 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 parameterless read tool with safety annotations fully covering the side-effect profile, the description supplies the right preconditions and rate-limit etiquette. It is slightly incomplete in not indicating what limit values or fields come back, which matters since no output schema is provided.

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 with a trivially complete (100%) schema, so the baseline of 4 applies; there is nothing for the description to add here and it correctly adds nothing.

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?

Specific verb (read) plus specific resource (sending limits), scoped by the negative space 'Does not send, reserve capacity or consume sending quota', which cleanly separates it from voidmail_send_email, voidmail_send_once and voidmail_send_status. An agent can identify the tool's role without opening any schema.

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?

'before planning email work' gives a clear trigger condition for when to call it, and 'Respect Retry-After; never split work across accounts to evade limits' adds operational guidance. No alternative sibling is named explicitly nor is a when-not-to-use case given, so it stops short of a 5.

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