gmail_messages_get

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the description does not need to reiterate that this is a safe read operation. However, the description adds no behavioral details beyond what annotations provide (e.g., response format nuances, potential errors). With annotations covering the safety profile, a score of 3 is appropriate—the description is consistent but does not enrich behavioral understanding.

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 a single, front-loaded sentence with no filler. It conveys the core purpose efficiently. While it could benefit from a bit more detail, for a simple get operation it is appropriately concise and structured.

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?

Given the tool's low complexity, full schema coverage, and read-only annotations, the description is largely sufficient. The only missing element is an indication of what the response contains (no output schema), but this is not critical for a standard message retrieval and is likely inferable from the tool's purpose. Overall, it is complete enough for an agent to invoke correctly.

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?

The input schema describes all three parameters (id, format, userId) with 100% coverage, so the description does not need to add parameter details. The description itself offers no additional meaning beyond the schema. Baseline 3 is correct when the schema handles parameter documentation.

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 clearly states the action ('Get'), the resource ('a single Gmail message'), and the key qualifier ('by ID'). This precisely differentiates it from siblings like gmail_messages_list (which lists multiple messages) and gmail_threads_get (which targets threads). An agent can unambiguously understand the tool's scope.

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?

The description implies usage for fetching a specific message by ID, but it does not explicitly state when to choose this over gmail_messages_list or mention any exclusions (e.g., 'use gmail_messages_list to fetch multiple messages'). The intended context is clear from the tool's name and sibling set, but explicit guidance is absent.

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