Schedule a pending send

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

Beyond the annotations, the description explains that this action does not queue anything immediately and only determines when an approved message is delivered. It also clarifies the future timestamp requirement. This adds useful behavioral context consistent with the idempotentHint and non-destructive annotations.

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 tight, front-loaded sentences with no filler. The core action, key behavioral caveat, and constraint are all stated efficiently.

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 two-parameter tool with no output schema, the description covers the essential operational context: it applies to pending approval sends, does not queue until approval, and requires a future send_at. It could mention what happens on repeated calls or error conditions, but the low complexity makes this adequate.

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 both parameters are already documented. The description reiterates the future-time requirement for send_at and references approval_id implicitly through 'waiting for human approval', but adds little beyond the schema.

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 uses a specific verb ('Set') and a precise resource ('delivery time of a send that is waiting for human approval'), and further clarifies that it only schedules an approved message rather than queuing it. This clearly differentiates it from siblings like schedule, approval_decide, and approval_review.

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 gives clear context: the tool is for sends waiting for human approval, and it explicitly notes that nothing is queued until approval. It also states the future-time constraint. It does not explicitly name alternative tools or say when not to use it, but the context is sufficient for most agents.

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