Get raw message source

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

Annotations already indicate read-only and idempotent behavior. The description adds a key behavioral detail: on IMAP, the message must be available offline or the tool will error rather than return partial data. This goes beyond annotations but could still benefit from mentioning authentication requirements or rate limits.

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, front-loaded with purpose and followed by an essential behavioral note. No filler or redundant 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?

Given the output schema exists, the description covers the core functionality and key constraint (IMAP offline requirement). It is sufficient for the tool's complexity but could mention the return format or edge cases for completeness.

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 0%, and the description provides no explanation of the two parameters (message_id, decrypt). It does not clarify the meaning of decrypt or the format of message_id, leaving the agent to rely solely on the schema which lacks descriptions.

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 uses a specific verb ('Fetch') and resource ('raw RFC 5322 source'), clearly distinguishing it from siblings like mail_get (which returns parsed message). The phrase 'for header forensics' further clarifies its specialized use case.

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 provides clear context ('for header forensics') and a practical constraint on IMAP ('needs the message to be available offline'). It implicitly guides the agent to use this when raw source is needed, avoiding alternatives like mail_get. However, it lacks explicit when-not-to-use or alternative tool names.

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