Get message by id

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

The readOnlyHint and openWorldHint annotations already establish the safety profile, so the description does not need to repeat that. It adds minimal behavioral context beyond the fetch action, such as not disclosing error handling for invalid IDs or the return shape for multiple messages, but it does not contradict the annotations.

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?

A single sentence with no filler, directly stating the action and scope. Ideal size and front-loaded 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?

For a simple read-and-fetch operation, the description covers the core functionality. It lacks explicit output shape, but without an output schema the 'Fetch' verb sufficiently implies the return. Given the tool's low complexity, the description is adequate.

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 only 33% (only 'peer' has a description). The description confirms ids are message IDs but does not clarify accountId or provide details about the ids array format beyond what minItems/maxItems already convey. It fails to compensate for the low schema coverage.

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 the specific verb 'Fetch' and identifies the resource (messages), scope (from a dialog), and method (by their ids). This clearly distinguishes it from sibling tools like list_messages or search_messages, which serve different purposes.

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 clearly implies usage when the agent has specific message IDs and knows the dialog (peer). However, it does not explicitly exclude alternatives or name sibling tools like list_messages, stopping short of a 5.

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