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

Annotations declare destructiveHint=true and idempotentHint=false; the description adds real behavioral context beyond that — that a shortened deadline actively ends signing when it passes (the destructive consequence), the one-hour minimum validation rule, and the null-removal escape hatch. It stops short of explaining permissions or what a successful response contains, but the key mutating side effect is disclosed.

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 sentences with no filler; the primary set-operation with its constraint is front-loaded, and the removal case plus the failure condition follow compactly.

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 3-parameter mutation with full schema coverage, no output schema, and annotations carrying the safety profile, the description covers validation, side effects, and the clear-deadline path. Only peripheral details (permission requirements, behavior on already-passed-but-open deadlines beyond the one-hour rule) are absent.

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 the baseline is 3, but the description adds meaning the schema does not: the strict one-hour-in-the-future floor and the explicit statement that null removes rather than merely 'sets' the expiration. document_id and assignment_id remain just identifiers, which the schema already handles.

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 and resource — setting/removing the deadline on an existing signature-request assignment — plus the dual mode (set vs. remove with null). No sibling tool touches assignment expiration, so it is unambiguously distinguishable from create_assignment or send_pdf_for_signature.

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?

Gives concrete preconditions: the timestamp must be ISO 8601 and at least one hour in the future, and 'expires_at: null' is the way to clear it. It also states the operation is refused on expired or closed requests, which tells the agent when the call will fail. It does not name an alternative tool, but no sibling provides equivalent functionality.

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