get_document_thumbnail

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

The readOnlyHint annotation already signals this is a safe read operation一味 The description adds value by disclosing the response format in detail (base64-encoded WebP image resource), which is helpful given there is no output schema. It does not cover error cases or size limits, but for a simple read-only fetch the disclosure is reasonable.

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?

The description is two short sentences with no filler. It front-loads the action and resource, then provides the key output detail. Every word earns its place.

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 one-parameter, read-only, simple fetch tool, the description provides the essential purpose and the return format, compensating for the missing output schema. It is complete enough for an agent to select and invoke the tool correctly, though it could mention that the ID is specifically a document ID.

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 says 'id' is a number, with no description. The main description clarifies that this ID selects a document whose thumbnail will be retrieved, giving the parameter its purpose and context. This meaningfully compensates for the 0% schema description coverage, though it could have been more explicit by naming it the document ID.

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 verb ('Get'), a resource ('document thumbnail'), and the input ('by ID'), and adds the output format ('base64-encoded WebP image resource'). It does not explicitly differentiate from sibling tools like get_document_preview, which is a close alternative, so it stops short of a 5.

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 implies when to use the tool: whenever a thumbnail image of a document is needed. However, it provides no explicit guidance about when not to use it, nor does it mention alternatives such as get_document_preview or get_document_content, leaving some routing ambiguity.

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