Get a Gmail thread

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

Annotations already mark readOnlyHint=true, indicating safe read. The description adds value by specifying that it returns 'every message's headers and decoded body text,' which is behavioral detail beyond the annotation.

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 sentences, both front-loaded with essential information. The first sentence states the function and scope; the second gives a usage hint. No wasted words.

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 fetch-by-ID tool, the description covers what is returned (headers and body). It does not mention pagination or size limits, but for a single thread, this is likely complete. The lack of an output schema is compensated by the description.

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% with well-described parameters for account and threadId. The description does not add new parameter semantics beyond what the schema provides, so baseline 3 is appropriate.

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 a full Gmail thread by thread ID, including every message's headers and decoded body text.' It uses a specific verb (fetch) and resource (full Gmail thread) and distinguishes from siblings like get_message (single message) and search_threads (finding thread IDs).

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 advises 'Use search_threads first to find the thread ID,' providing clear context for when to use this tool. It does not explicitly mention alternatives like get_message, but the instruction is sufficient to guide the agent.

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