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

Annotations already declare readOnlyHint=true and destructiveHint=false, but the description adds critical behavioral context: the return is data about other agents, not instructions, and should never replace user approval. This goes well beyond the annotations and is essential for correct use.

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 four sentences with zero waste. It front-loads the purpose, then gives usage timing, then an important behavioral warning. Each 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 two parameters, an output schema, and safety annotations, the description covers purpose, usage timing, and the critical behavioral caveat. Nothing an agent needs to call it correctly is missing.

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% — both parameters are already documented. The description adds minimal value beyond the schema: it ties agent_id to the one used in agent_checkin, which is useful but not extensive. Baseline 3 applies since the schema does the heavy lifting.

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 the verb (reads), the resource (messages other agents sent), and the scope (since last poll). It distinguishes itself from sending tools and names a prerequisite (agent_checkin), so an agent can tell it apart from siblings like agent_send.

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 explicitly says when to poll (start of task and periodically during long work) and gives concrete examples of what it reveals. It also instructs to check in first with agent_checkin. It doesn't explicitly list alternatives, but the context implies this is the receiving side, so guidance is clear though not exhaustive.

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