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

Annotations already flag destructiveHint=true and openWorldHint=true, but the description adds real value on top: it sends 'in the same thread' and 'from the address they wrote to', disclosing threading and sender behavior an agent could not infer from the schema. 'Cannot be recalled' reinforces irreversibility, though send failure modes and rate limits are unaddressed.

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?

Two tightly written sentences with the primary action first and the irreversible consequence second. Nothing is repeated and no sentence is filler.

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-required-parameter send tool with a rich annotation set and no output schema, the description supplies the essential extras: thread continuity, sender address, and the irreversibility warning. An agent has enough to invoke this 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 coverage is 100%, so both parameters are already documented as 'The reply's id' and 'The answer to send'. The description adds only marginal framing ('the founder's answer') and no format, length, or content constraints, which is the expected baseline when the schema does the work.

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 gives a concrete verb ('Send'), resource ('the founder's answer'), and recipient scope ('a prospect who replied'). It is clearly not a drafting tool, distinguishing it in spirit from draft_outreach_emails, but it never names a sibling to route against explicitly.

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 trigger condition is stated plainly: use this when a prospect has replied and the founder's answer should go out. It does not spell out when-not conditions or name an alternative tool, so it falls 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.