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

Beyond the readOnlyHint and idempotentHint annotations, the description adds meaningful behavioral context: it reads immediately without waiting, the heartbeat ID is a 256-bit bearer secret, and no authentication is required. These details clarify security expectations and non-blocking behavior without contradicting 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?

The description is compact and front-loaded with the core action. Each sentence earns its place: what the tool does, what it inspects, the non-waiting behavior, and the security-relevant bearer-secret/no-auth clarification. There is no filler or repetition of schema details.

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 single-parameter read-only tool with an output schema, the description covers the essential context: what state information is available, that it is non-blocking, that the ID is a secret, and that authentication is not required. Nothing an agent needs to decide whether to call this tool 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% and the single parameter is already described as the secret heartbeat ID returned by create_heartbeat. The description adds further meaning by emphasizing that the ID is a 256-bit bearer secret and that no authentication is required, which goes beyond the schema and helps the agent handle the parameter correctly.

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 opens with a specific verb and resource ('Read one heartbeat immediately') and then enumerates exactly what can be inspected: armed, missed, fired, expired, running late, and next deadline. This distinguishes it from the sibling create_heartbeat and ping_heartbeat by focusing on immediate status inspection rather than creation or waiting.

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 states the intended use ('Use it to inspect whether...') and explicitly notes that it does not wait for a state change, which guides an agent away from using this tool for blocking or state-transition waiting. It does not name a specific alternative tool, so it stops short of a full 5.

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