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

readOnlyHint=true already covers the safety profile, but the description goes further by enumerating the three return states ('running', 'replied' with reply text, 'failed'), which is the key behavioral fact for a polling tool with no output schema. It doesn't cover edge cases like an unknown/expired trace_id or eventual expiry of the reply.

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 tight sentences with the core action front-loaded, then return states, then polling cadence. No filler or redundancy.

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 one-parameter read/poll tool with annotations covering safety and no output schema, the description supplies the missing return-state semantics and polling guidance an agent needs. Only minor gaps remain (behavior on invalid trace_id, whether replies persist).

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% and the single parameter's description already states it is 'The trace_id message_agent returned.' The description repeats that origin but adds no format, length, or validity detail beyond the schema, so baseline 3 applies.

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?

States a specific verb (read) and resource (an agent's reply), and ties it directly to the sibling that produces the input: 'Read what an agent answered to a message_agent call.' An agent can distinguish this from message_agent and other read tools without opening the schema.

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?

Clearly establishes the usage context (call it after message_agent, using the trace_id that call returned) and gives explicit cadence guidance ('Wait at least a minute between checks'). It stops short of stating when NOT to use it or what to do on repeated 'running'/'failed' states, so no full when-not/alternatives coverage.

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