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

Annotations already establish readOnly, idempotent, and non-destructive behavior, so the bar is lower. The description adds two things annotations don't cover: that calls are free (cost context for autonomous agents) and the scope of the return value (status only, no earnings data). It stops short of saying which status values are possible.

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 cost signal and the core question, with the return-value caveat last. The 'Free.' fragment is terse but earns its place as a cost signal; nothing is redundant.

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?

With a single parameter, no output schema, and rich annotations, most of the burden is already met, and the description usefully discloses that only status is returned. However, it omits both the input format for the code and any indication of what statuses come back, which matters since no output schema exists.

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?

There is one parameter at 0% schema description coverage, so the description carries the full burden and does not compensate at all. It never explains what a 'code' looks like, whether it is case-sensitive, or what form to pass, leaving the only input undocumented.

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 states a specific check on a specific resource: whether a ref code is valid and active. It also implicitly distinguishes itself from partner_stats by noting 'no earnings', so an agent can tell it isn't the metrics tool, though the check verb is phrased as a question rather than stated directly.

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 rather than stated: 'Returns the code status only (no earnings)' hints that earnings questions belong in partner_stats, and 'Free' signals low-cost invocation. No explicit when-to-use, when-not, or named alternative is given, so the agent must infer the routing.

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