Get message headers

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

Annotations already declare readOnlyHint=true and openWorldHint=true. The description adds value by revealing that the tool returns parsed verdicts and Proton metadata, and that raw=true returns the unparsed header block. No contradiction with annotations.

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-load the core purpose and then add the most important parameter behavior. Every sentence contributes meaningful information with no filler.

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?

With no output schema, the description appropriately summarizes return content (headers, verdicts, metadata) and the raw mode. It could be more complete by clarifying uid/uidvalidity semantics, but for a read-only header tool this is largely sufficient.

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 only 50% (raw and folder have descriptions, but required uid and uidvalidity do not). The description does not compensate by explaining uid or uidvalidity; its only parameter-related addition, 'Pass raw=true for the unparsed header block,' largely restates the schema's description of raw.

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 tool fetches message headers plus SPF/DKIM/DMARC verdicts and Proton metadata for authentication judgment. This specific verb+resource combination distinguishes it from siblings like read_message or list_attachments.

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 phrase 'for judging whether a message is what it claims to be' provides a clear use case and implicitly positions this tool for message validation. It does not explicitly name alternatives or when-not-to-use, so it stops short of a 5.

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