gmail_read_message

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the agent knows this is a safe read operation with no side effects. The description adds the behavior of returning the full message with plain-text body, which is useful context beyond annotations. It doesn't mention HTML body handling, attachments, or headers, which would be richer context, but with openWorldHint the agent is told not to assume completeness.

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 efficient sentence with zero waste. It front-loads the verb and resource immediately. Every word earns its place, though it could arguably have added brief parameter detail without hurting 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?

The tool has an output schema present, so return values don't need description coverage. However, with 0% schema description coverage on 2 parameters, the description leaves message_id semantics and account handling entirely to the agent's inference. For a straightforward read tool, this is adequate but not rich. openWorldHint partially mitigates completeness concerns.

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 0%, so the description must carry the parameter-load. However, the description adds no parameter-specific explanation — it doesn't describe what message_id format is expected or what the account parameter does. With 2 params and 0% schema coverage, the description should compensate more but doesn't.

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 'Fetch one message in full, including its plain-text body' — a specific verb (fetch) targeting a specific resource (one message) with the scope of full content including body. It doesn't explicitly differentiate from siblings like gmail_search or gmail_list_recent, but the singular-message fetch is distinct enough from those list/act tools.

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 this is for retrieving a specific single message by ID ('one message in full'). It doesn't explicitly state when to use vs alternatives, but the sibling tools (list, search, draft/send/label) are clearly different action types, so the use case is reasonably implied. No exclusions or when-not guidance is given.

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