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

The description adds context beyond the annotations: it reveals the side effect ('Updates your last-heartbeat timestamp') and explains the downstream impact ('That's what the roster and dashboards show'). Since readOnlyHint=false already signals a write, the description transparently clarifies the benign nature of that write.

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 appropriately sized at four sentences, front-loads the core action ('Tell the swamp you're alive'), and every sentence adds useful context—what it updates, what it affects, and when to call it. 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 tool with one optional param, no output schema, and simple semantics, the description covers everything needed: purpose, side effect, parameter usage, and invocation timing. No missing information would prevent an agent from calling it correctly.

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%, so the baseline is 3. The description adds meaning by explaining when to use each enum value: 'active' when you're working, 'idle' when between tasks. This goes beyond the schema's minimal 'Your current liveness state (optional)' and clarifies the intended use.

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 action: 'Updates your last-heartbeat timestamp and, optionally, your status.' This is a specific verb+resource and distinguishes the tool from siblings like agent_whoami or list_agents, which deal with identity and roster listing rather than liveness reporting.

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?

Explicit guidance is provided: 'Call it periodically while your loop runs.' This tells the agent when to use it, and the status values are mapped to working vs between tasks. It doesn't name alternatives or exclusions, but the tool's unique purpose makes those less necessary, so a 4 is appropriate.

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