Read a Gmail message's full body

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

With no annotations provided, the description carries the disclosure burden. It discloses read-only nature ('Read-only'), explains behavior with thread_id ('reads the most recent message in that thread'), and clarifies the precedence when both parameters are given. While it doesn't discuss authentication or side effects, the read-only declaration and behavioral details are valuable for this simple tool.

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, front-loaded with the primary purpose, then providing usage context and parameter guidance. Every sentence provides functional value; no filler or redundant information.

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?

This is a simple 2-parameter read tool with no output schema. The description covers what it does, when to use it, how parameters interact, and its read-only nature. For the given complexity, it is complete and leaves no obvious gaps for an agent to correctly select and invoke the tool.

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%, so the parameters are already documented. The description adds meaningful relationship semantics: it explains that message_id comes from a search/scan result, that thread_id reads the most recent message, and that thread_id is ignored if message_id is given. This goes beyond the schema's standalone descriptions.

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 opens with a specific verb+resource: 'Read the full body of ONE specific Gmail message.' It clearly distinguishes from sibling tools by stating that search_gmail_for_job and scan_job_updates only return snippets, while this tool provides the full content.

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?

Explicitly states when to use: 'use this when you need the actual content (e.g. an interview link or instructions).' It also names the alternatives (search_gmail_for_job, scan_job_updates) and explains their limitation, providing clear context for selecting this tool. Additionally, it provides parameter usage guidance (message_id vs thread_id).

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