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

Annotations already declare this is a non-destructive, non-open-world write (readOnlyHint=false, destructiveHint=false), and 'cheap signal' adds useful cost/frequency context. The description does not explain what is actually persisted, whether signals expire, or any rate-limit expectations for what is effectively a status ping.

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?

Two short sentences, front-loaded with the core purpose and the two triggering cases. 'Cheap signal' is slightly informal but carries real information about cost; nothing is padded.

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?

A simple, fully optional three-flag ping with complete schema coverage and annotations covering the safety profile needs little more. The only gap is the undocumented 'private' flag, which is not a blocker for correct invocation.

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 all three flags are already documented in the schema. The description reinforces the meaning of ai and git but says nothing about the private flag or how the flags interact when combined, so it adds little beyond the schema.

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 names a concrete effect (sends a cheap signal that the AI is working or that you committed, lighting a live badge), which is more specific than the bare name 'heartbeat'. It does not, however, distinguish this from other status/activity siblings such as set_status or activity.

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?

Usage is implied by the parenthetical labels: use it when the AI is actively working (ai) or right after committing (git). There is no explicit statement of when not to call it, how often to call it, or why one would choose this over set_status or activity.

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