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

Annotations already establish readOnlyHint=false and destructiveHint=false. The description adds meaningful behavioral context beyond that: the auth requirement ('owner-authenticated', 'Use the agent-specific key, not X-Autonet-Token') and a misuse boundary. It stops short of describing what server-side state the heartbeat updates, but the added context is genuinely useful.

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 sentences, each earning its place: primary action and scope, auth key selection, and a misuse warning. The core purpose is front-loaded, with no filler or repetition of schema/annotation content.

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 2-parameter tool with an output schema present, the description covers purpose, usage context, auth specifics, and exclusions. The only gap is the unspecified server-side effect of a heartbeat on agent health state, which is minor given the output schema and annotations already carry the remaining burden.

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 description coverage is 0%, so the description must compensate. It does so for api_key with the critical clarification 'Use the agent-specific key, not X-Autonet-Token', which prevents a common auth mistake. The agent_id parameter, however, is left only to the schema title 'Agent Id' with no additional guidance on format or source.

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+resource: 'Send an owner-authenticated heartbeat from the actual worker loop'. The explicit exclusion 'does not replace endpoint checks' differentiates it from sibling tools like agent_health_checks and agent_endpoint_assessment. An agent can tell what this tool is for 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?

Gives an explicit when ('from the actual worker loop') and explicit when-nots ('does not replace endpoint checks', 'Never send a heartbeat to pretend a failed worker is alive'). It also provides a routing hint by distinguishing heartbeat signaling from endpoint checks, which are presumably handled by sibling tools.

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