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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=true, so the safety profile is fully carried by structured data. The description adds only the field inventory of the response, which is arguably redundant given an output schema exists, and says nothing about auth requirements, error cases (missing inbox/message), or rate limits. Adds some context but not much beyond structured fields.

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?

The core purpose is a single front-loaded sentence with no waste. However, the appended pricing boilerplate block is tool-agnostic metadata that does not earn a place in a description intended to drive invocation, diluting the structure.

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 simple two-parameter read tool with full schema coverage, complete annotations, and an output schema, the description covers what an agent needs to call it correctly. Return-value detail is present but redundant since the output schema handles it; the only real gap is sibling disambiguation.

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 100% and both parameters (inbox_id, message_id) are documented in the schema, so the baseline is 3. The description does not add any format, ID-source, or constraint detail beyond what the schema already states.

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?

The description gives a specific verb ("Retrieve detailed information") and a precise resource ("a specific message within an inbox"), and enumerates the returned fields (sender, recipients, content, labels, attachments, timestamps). It distinguishes adequately from the list sibling get_agentmail_inbox_messages by saying "a specific message," but never explicitly differentiates from get_agentmail_inbox_message_raw or get_agentmail_inbox_message_attachment.

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 guidance and no alternatives named, even though the sibling set contains get_agentmail_inbox_message_raw, get_agentmail_inbox_message_attachment, and get_agentmail_inbox_thread. The purpose implies "fetch one message by ID," but nothing routes the agent among these near-identical retrieval tools.

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