get_message

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

The annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds useful behavioral context by noting that the response includes body and attachment metadata, and by warning that PLAIN_TEXT helps avoid context exhaustion. It does not cover error behavior, but with annotations present this is a strong addition.

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, no wasted words, with the core purpose front-loaded and the alternative and format recommendation following immediately. Every sentence earns its place.

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 simple read tool with no output schema, the description supplies enough to call it correctly: the id-based single-message scope, the sibling alternative, and a format recommendation. Minor gaps remain around per-format return differences and error behavior, but the schema already covers the format details.

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 baseline would be 3, but the description adds meaning beyond the schema by tying PLAIN_TEXT to a concrete rationale: preventing context exhaustion. The schema itself documents the enum modes thoroughly, so the description complements rather than repeats.

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 uses a specific verb and resource ('Retrieves a single email message by id') and explicitly distinguishes this tool from the sibling get_thread by noting that get_thread is for whole conversations. An agent can immediately tell what this tool does and when it differs from the conversation-level alternative.

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?

It states the key usage condition directly: use get_thread for whole conversations, implying get_message for single messages. It also gives explicit parameter guidance by recommending PLAIN_TEXT to prevent context exhaustion, which is actionable and reduces misuse.

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