Get a message's full content

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

No annotations are provided, so the description must carry the full behavioral burden. It does describe the return content and the operation as a fetch, which strongly implies read-only behavior. However, it does not explicitly rule out side effects such as marking the message as read, nor does it describe error behavior or access requirements.

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 one concise sentence with no filler. It front-loads the main behavior and includes the essential parameters needed to invoke the tool.

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 two-parameter retrieval tool with full schema coverage, the description is largely complete. It explains what will be returned (text and HTML body) even though there is no output schema. It would benefit from clarifying whether fetching affects message state, but everything else an agent needs to call it is present.

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 coverage is 100%, so the schema already documents both parameters, their types, and the UID's source. The description mentions folder and UID but adds no new parameter semantics beyond restating the identifiers.

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 clear verb ('Fetch'), a specific resource ('full content (text and HTML body) of a single message'), and the identifying inputs ('folder and UID'). This distinguishes it from siblings like list_messages, which lists messages rather than retrieving one message's full content.

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 the tool is for retrieving a single message's full body, but it does not explicitly state when to choose this over list_messages or any other sibling. The schema does note that UID comes from list_messages, but the description itself provides no direct when-to-use or when-not-to-use guidance.

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