Read one Gmail message

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

No annotations are provided, so the description carries the full behavioral burden. It usefully discloses that the body is returned already decoded, but says nothing about side effects (does reading mark the message as read?), auth requirements, rate limits, or what else is returned besides the body — notable given siblings like gmail_mark_read imply state-changing operations exist.

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?

Two short sentences, fully front-loaded: the core action first, the routing guidance second. Nothing is redundant with the schema or the title.

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?

There is no output schema and no annotations, so the description must carry more than it does. It mentions the decoded body and implies truncation, but never describes the shape of the response (headers, metadata, attachments) or any state side effect, leaving gaps for an agent that needs to know what it will actually receive.

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 100%, so both parameters (id, maxChars with default and bounds) are already fully documented in the schema. The description adds no syntax or constraint detail beyond what's there, which is the expected baseline when the schema does the heavy lifting.

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 ('Fetch a single Gmail message') and adds a meaningful qualifier ('with its decoded body text') that tells the agent no further decoding is needed. The second sentence separates it from the list-style sibling gmail_fetch_recent, so an agent can route between the two without opening a 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?

Gives clear selection context: use it after gmail_fetch_recent when a snippet is insufficient to decide what to do, which names the alternative and the trigger condition. It stops short of stating explicit exclusions or prerequisites (e.g. that the id must come from that fetch, or when the full body is unnecessary).

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