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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds only the endpoint path and the note that including content yields HTML and plain text; it says nothing about what is returned by default or error behavior for a missing id.

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?

Three short sentences, front-loaded with the core purpose and then the content flag. Nothing is padded, though the raw endpoint reference is marginally redundant for an agent that already has the tool name.

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 two-parameter read with no output schema, the description omits the shape of the returned message object (fields beyond body_html/body_text) and any not-found behavior. Adequate but leaves the agent guessing about return structure.

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 50%: include_content is already fully documented in the schema, and message_id, while undocumented, is self-evident from its name and required status. The description restates the include_content effect (HTML plus plain-text body) but adds no format, size, or default-value detail beyond the schema.

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 states a single resource retrieval scoped by id and names the underlying endpoint (GET /messages/{message_id}), which distinguishes it from list_messages and get_message_sender_defaults. The verb is implicit ("One message by id") rather than explicit, but the intent is unambiguous.

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?

Usage is only implied: the agent must already have a message_id to call it, and the mention of include_content=true hints at when to request bodies. No alternatives (e.g. list_messages for discovery, get_message_sender_defaults) or when-not conditions are named.

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