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

Annotations already declare readOnlyHint and idempotentHint, so the safety profile is covered. The description adds fresh behavioral context: incomplete envelopes error, the PDF is returned as base64, and an Authorization Bearer token is required. This goes beyond the structured annotations without contradicting them.

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?

Four short sentences deliver purpose, parameter provenance, failure mode, return format, and authentication requirement. Every sentence adds value, and the primary purpose is front-loaded. There is no filler or repeated schema content.

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 single-parameter read-only tool, the description covers the key operational facts: what it downloads, when it is valid, what input to use, what errors occur, the return format, and the required auth. The output schema exists, so explaining return shape in detail is unnecessary. Nothing critical is missing.

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 schema only defines document_id as a required string with no description, so 0% schema description coverage. The description compensates fully by specifying that document_id must be the original document_id from send_envelope / get_envelope_status / list_envelopes, and explicitly excludes completed_document_id. This is essential disambiguation that the schema alone cannot provide.

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-resource pairing: 'Download the standalone Certificate of Signature PDF for a completed envelope.' This clearly distinguishes the tool from the sibling download_signed_document, which downloads a different artifact. The statement about using the original document_id rather than completed_document_id further sharpens the tool's identity.

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 when-to-use context: only for completed envelopes, and it explicitly warns that incomplete envelopes produce an error. It also states which source to use for document_id. However, it does not explicitly name an alternative such as download_signed_document, so the reader must infer the comparison from the certificate wording.

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