mail_read

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

Annotations already declare readOnlyHint and destructiveHint=false, yet the description adds real substance: the untrusted-content trust boundary, the ordering of returned data (headers and attachment list before body), and that the body is plain text wrapped in markers. This is exactly the extra context an agent needs to handle email safely.

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 dense sentences with zero filler, and the read-only constraint plus the injection warning are front-loaded before the mechanics. Slightly dense packing of unrelated concerns, but nothing wasted.

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 usefully sketches the return shape (headers, attachment list, body in markers). The main gap is the absence of any mention of truncation or the maxChars limit, which affects interpretation of the returned body.

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%, so the description must carry parameter meaning. It clarifies that 'ref' identifies a single message, but says nothing about 'maxChars' (a default-20000 truncation control, crucial for body reads), leaving one of two parameters undocumented.

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 and resource: 'Reads one message by ref', which is clearly distinct from listing mailboxes or searching. It does not explicitly name the sibling tools, so sibling differentiation is implied rather than stated.

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?

Usage is implied: you need a message ref, presumably obtained from mail_search or mail_list_mailboxes. However, it never says when to prefer this over mail_search or what to do if the ref is unknown, and no alternatives or exclusions are named.

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