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

With annotations already declaring readOnlyHint=false and idempotentHint=true, the description adds crucial extra behavior: the insufficient_credits refusal carrying a top_up_url for the user, and the idle effect of restarting an active tracker. It maps directly to the idempotentHint, and there is no contradiction with 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?

Three concise sentences that front-load the primary action, then cover the conditional immediate-survey behavior, the credit error handling, and idempotency. No fluff; every sentence adds value.

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 mutation tool with no output schema, the description covers the main behavior, the conditional trigger, the idempotent nature, and the most important error case (insufficient credits) including how to guide the user. An agent has enough to call it correctly and handle the failure path.

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?

The schema already describes tracker_id fully ('The UUID of the tracker: call list_trackers to find it.'), so coverage is 100%. The description does not add parameter-specific details beyond that, meeting the baseline 3 for high schema coverage.

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 uses a specific verb ('start'/'restart') and a clear resource ('measurement of a tracker against the prepaid credit balance'), and distinguishes itself from siblings like 'survey_now' and 'pause_tracker' by specifying the immediate-survey behavior and idempotency. The agent can tell exactly what this tool does and what it does not do.

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 explicitly states when the first survey runs ('there and then' unless a future next_survey_at exists) and that starting an active tracker changes nothing. This implies the agent should use a different tool (e.g., survey_now) for an unconditional immediate survey, though it does not name an alternative directly. Clear context without explicit 'use X instead' guidance.

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