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

Annotations already declare readOnlyHint=true, so safety is covered. The description adds real value beyond that: it discloses that the returned passport is cryptographically signed with an ES256 JWS and includes on-chain hashes and Stripe ids. It does not cover error/precondition behavior (e.g. what happens if the invoice is missing or unsigned).

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?

One sentence, front-loaded with the verb and resource, followed by the payload contents. Efficient, though the dense parenthetical of evidence types could be trimmed or split for readability.

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-param read tool with no output schema, the description substantially documents the return payload (signed JWS proof and evidence fields), which is exactly what the absent output schema would otherwise need to carry. Only usage/precondition guidance 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?

There is a single invoice_id parameter with UUID format, and schema description coverage is 0%. The description implies it identifies the invoice whose passport is fetched but adds no detail on format or validation beyond what the name conveys; with only one obvious param, this is adequate but not enriched.

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 ('Get') and a distinctly named resource ('Invoice Passport') and enumerates its contents (invoice, parties, payment evidence, history, JWS proof). This clearly separates it from get_invoice or get_efactura_xml in spirit, though it never names a sibling to make the distinction explicit.

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?

There is no when-to-use or when-not-to-use guidance, nor any mention of prerequisites (e.g. must the invoice exist, must it already be signed). The agent must infer that this is the signed-bundle counterpart to get_invoice without being told.

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