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

Annotations already declare the safe read-only profile, but the description adds real behavioral content: the body is decoded, HTML-only messages are down-converted to plain text, and attachments are returned as metadata with the attachmentId consumed by two named sibling tools. It does not mention auth requirements or attachment-size limits, but the added context is substantive.

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 sentences, front-loaded with the core action and scope, then behavior, then the prerequisite. Every clause either distinguishes the tool or changes how an agent calls it; nothing is redundant.

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 carries the return-shape burden and does explain body and attachment fields. It omits other likely returned metadata (headers, subject, labels), which is a minor gap for a single-message read.

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 67% and messageId has no schema description at all; the description compensates by explaining where that ID comes from. maxChars and mailbox are covered by the schema, so the description's remaining contribution is the attachmentId/parameter linkage.

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?

"Read one message in full, including its decoded text body and its attachments" names a specific verb, resource and scope, and implicitly separates it from get_gmail_thread (whole thread) and list_messages (envelopes). An agent can identify the right tool without opening the schema.

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?

It gives a clear workflow precondition: get the message ID from search_gmail_messages, which tells the agent this is the step after a search. It does not state when to prefer get_gmail_thread or get_outlook_message instead, so no explicit exclusion is offered.

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