read_message

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

The description indicates a non-destructive read operation but does not disclose additional behavioral traits like encoding, size limits, or authentication needs. With no annotations, the description carries the burden but provides minimal extra transparency beyond the obvious.

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 concise with no redundant words, front-loads the main purpose, and uses a clear parameter list. Every sentence adds necessary 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?

The description covers both parameters well and, given the existence of an output schema, does not need to detail return values. However, it omits discussion of potential encoding or attachments, leaving room for ambiguity.

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 description adds key meaning: message_id is an IMAP sequence number from list_messages, and folder specifies the IMAP folder (default INBOX). This goes beyond the schema's type-only definitions, compensating for 0% schema coverage.

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 clearly states the verb 'read' and the resource 'full body of a specific email', distinguishing it from siblings like list_messages (listing headers) and search.

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?

It explains how to obtain the message_id (from list_messages) and the folder parameter, implying when to use the tool (when you need full email body). It lacks explicit when-not or alternatives, but the context is clear.

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