read_message

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

The description is otherwise informative about return shape and conditional side effects, but it discloses that mark_read=true marks the message read. That optional mutation contradicts the annotation readOnlyHint=true, which declares the tool read-only.

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 description is front-loaded with the core action and then compactly lists output details and the mark_read condition. It is appropriately sized with no wasted sentences.

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 explains the return payload: headers, text body conversion, attachment metadata, and flags. It is nearly complete, but it omits interactions such as max_chars/include_html and the mode prerequisite noted in the schema for mark_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 75%, and the schema already documents id, mark_read, and max_chars. The description adds useful meaning about HTML-to-text body handling and the attachment list, but it does not clarify include_html or max_chars interactions beyond the schema.

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?

It states a specific verb and resource, "Read one message," and enumerates the returned payload: headers, body, attachment list, and flags. It does not explicitly distinguish itself from siblings such as get_thread or search_messages, so it is clear but not fully differentiated.

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 by "Read one message" and the conditional note about mark_read=true. However, it gives no explicit when-to-use guidance or alternatives, such as using get_thread for a conversation or search_messages to locate a message.

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