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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds substantial context beyond them: it makes no network or DNS calls, does not verify signatures, and does not store header text. These are exactly the operational facts an agent needs before routing sensitive email content here.

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?

Front-loaded with the core action, then a dense but useful enumeration of outputs and constraints. Slightly long, and the MailAlign API cross-reference is arguably incidental, but every clause carries information an agent can act on.

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 two-parameter read-only analysis tool with a full output schema and complete annotation coverage, nothing material is missing: inputs, outputs, side effects, and safety profile are all addressed.

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 both parameters are already well documented, including the body-after-blank-line behavior and the include_raw semantics. The description adds no parameter-level detail (e.g. it never mentions include_raw), so the baseline 3 applies.

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?

States a specific verb (analyze) and resource (raw email headers), and enumerates precisely what is reported: alignment, SPF/DKIM/DMARC/ARC verdicts, hop chain, and findings. No siblings exist, and the scope is unambiguous.

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 makes the input condition explicit ('pasted raw email headers') and draws clear negative boundaries ('makes no network or DNS calls and does not verify signatures'), which tells an agent when this tool is and isn't the right fit. It does not state an alternative route, but no sibling tools exist.

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