mail_read

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), so the bar is lower. The description still adds two things those annotations do not: the required automation:Mail permission and the scope restriction to the current inbox. It does not describe failure behavior for out-of-scope IDs, which keeps it from a 5.

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?

One compact sentence carries the operation, key, and scope, with the permission metadata bracketed at the end. Front-loaded and waste-free, though the version/permission tag is boilerplate that could be trimmed if the runtime already surfaces it.

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?

An output schema exists, so return values need no explanation, and this is a single-parameter read-only tool. Scope, key semantics, and auth requirement are all present; only the ID-provenance path (mail_search) and out-of-scope error handling are absent.

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% — the id parameter is a bare integer with an empty description. The phrase "numeric Mail ID" and "limited to current inbox scope" do clarify that the integer is a Mail ID scoped to the inbox, which is real added meaning, but the description doesn't explain how to source the ID or what happens if it isn't an inbox message.

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 ("Read one inbox message") and identifies the lookup key (numeric Mail ID), which clearly separates it from mail_search, mail_send, and mail_create_draft. It stops short of naming an alternative sibling explicitly, so it lands at 4 rather than 5.

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?

"limited to current inbox scope" implies when this tool is appropriate (inbox messages only) and implicitly excludes other mailboxes or search-driven retrieval. However, it never states how to obtain the ID or routes the agent to mail_search when the target isn't in the inbox, leaving usage to inference.

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