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

With no annotations, the description carries the full behavioral burden and largely drops it. "Runs the same code the tool page runs" is an implementation remark, not a disclosure of what the tool actually does — it doesn't say whether parsing triggers DNS lookups, validates SPF/DKIM/DMARC, or is purely syntactic; "Scope: dns" hints at network work but is never unpacked.

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?

Three short sentences with the purpose front-loaded, so structure is good and there is no bloat. The middle sentence about running the same code as the tool page is filler that consumes space without informing the agent.

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?

This is a simple one-parameter tool, but with no output schema the description should explain what comes back — parsed header fields, authentication verdicts, or DNS-derived results. Instead it leaves both the return shape and the meaning of "Scope: dns" entirely undefined.

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?

There is a single required parameter and schema description coverage is 100%, with the schema stating it is raw headers one per line, so the baseline is 3. The description adds nothing further about format expectations (e.g., whether a Received chain or full MIME header block is acceptable).

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?

"Parse raw email headers" gives a specific verb and resource, so an agent knows exactly what input it takes and what class of operation it performs. However, the sibling list contains several email-oriented tools (check_email, check_email_check, check_dkim, check_mx) and the description makes no attempt to distinguish this header parser from them.

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?

There is no when-to-use or when-not-to-use guidance and no named alternative, despite many adjacent email tools an agent could confuse this with. The fragment "Scope: dns" is unexplained jargon rather than an actionable condition for selecting this tool.

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