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

Annotations already cover the write and destructive nature (readOnlyHint=false, destructiveHint=true) and idempotency (idempotentHint=true). The description adds valuable behavioral context not in annotations: the tool only works before signing and only on editable fields, clarifying when an operation will fail. It does not detail the mutation semantics (e.g., whether existing values are overwritten), but annotations lower the burden.

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 purpose is first, followed by the usage condition, the preferred alternative, and the key limitation. Every sentence adds distinct value.

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?

The description covers purpose, usage timing, alternative tool, and an important precondition. The schema fully documents parameter semantics. For a 2-parameter write tool with no output schema, this is nearly complete; the only minor gap is not stating what the response indicates about success.

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 input schema already documents both parameters and even gives detailed per-type value rules with examples. The description adds no parameter-level meaning, but with full schema coverage the baseline 3 applies.

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 states a specific action ('Update form field values on an already-created document') with a clear resource and distinguishes it from the read sibling get_document_field_values by framing this as a write operation. It also differentiates from create_document by explicitly targeting documents that already exist.

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 explicit when-to-use guidance: only after document creation when values need to be added or corrected, and points to the preferred alternative (pass values upfront via create_document's fields parameter). It also states a hard constraint: 'Only works on editable fields before anyone has signed.'

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