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

Annotations already communicate read-only, idempotent, open-world, and non-destructive behavior. The description adds useful context beyond the annotations by disclosing that private-room access is checked and that the reply reference is included in the result.

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?

The description is two short, purposeful sentences. The main action is front-loaded, and the extra behavioral detail about private-room access is presented without unnecessary filler.

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 strong annotations, the description covers the core purpose and authorization context. However, it leaves parameter roles unstated and does not guide the agent toward or away from sibling tools, which creates a meaningful gap in completeness.

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?

The input schema has 0% description coverage, so the description must compensate for the meaning of the two required parameters. It does not explicitly explain that 'id' identifies the message and 'name' identifies the room or parent resource, though the private-room access line hints at this.

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 a specific action ('Read') and a specific resource ('a single message'), and adds the unique detail 'including its reply reference.' This distinguishes it from sibling tools like read_messages and reply, even without naming them explicitly.

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 singular 'single message' implies this tool is for one message rather than a list, so usage context is somewhat clear. However, it does not explicitly name alternatives like read_messages or state when not to use this tool, leaving some inference required.

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