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

Beyond the readOnlyHint, idempotentHint, and destructiveHint annotations, the description adds meaningful behavioral context: the visibility restriction, the base64 encoding of content, and the specific error/fallback behavior for oversized results. No contradiction with annotations exists.

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 concise sentences with no filler. The action and key output detail are front-loaded, and the error/fallback guidance is placed second. Every sentence carries useful information.

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 simple one-parameter, read-only tool with a full output schema and comprehensive annotations, the description covers the essential behavioral details: scope, output encoding, error condition, and fallback path. Nothing needed for correct invocation 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?

Schema description coverage is 100%, so the single attachment_id parameter is already fully documented in the schema, including its UUID format and source (upload_attachment). The description doesn't need to add parameter-level detail, so the baseline score of 3 is appropriate.

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 ('Fetch') and resource ('an attachment visible to this agent'), and clarifies the output format ('base64 content plus metadata'). This clearly distinguishes it from sibling tools like upload_attachment and delete_attachment by focusing on the retrieval operation.

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 explicitly provides a when-not-to-use condition: results over the connector size limit return attachment_too_large and should instead be fetched via the agent REST API. This gives the agent a clear routing decision without ambiguity.

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