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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description usefully sharpens this by saying only 'metadata' is returned (not the document image itself) and maps to the concrete endpoint, but says nothing about error behavior for invalid ids or what the metadata contains.

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 compact sentences with zero padding; the purpose is front-loaded and the endpoint detail follows as supporting context.

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 trivial one-parameter read tool with the safety profile already in annotations and no output schema, the definition is close to complete. The modest gap is that no output schema exists, so the description could say a bit more about what 'metadata' comprises.

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 single document_id parameter is already documented in the schema. The description adds no format, provenance, or sourcing guidance for the id beyond 'by id', which is baseline behavior when the schema carries the load.

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 ('Retrieve a single document's metadata by id') and clarifies the scope is one document, which separates it from onfido_list_documents. It stops short of naming any sibling explicitly, so an agent must infer the contrast with the list variant.

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 phrase 'by id' implies the precondition of already having a document_id, but there is no explicit when-to-use guidance, no when-not-to-use, and no mention of onfido_list_documents as the alternative for enumeration.

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