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

Annotations only indicate non-read-only and non-destructive. The description adds valuable behavior: the tool consumes one unit of the daily limit, must be called exactly once, and requires checking the `allowed` field to decide whether to continue. This exceeds what annotations convey.

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 sentences with no wasted words. The first sentence states the core action, and the second sentence fronts the exact call timing and conditional handling. Every sentence earns its place.

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 no output schema, the description bears responsibility for response semantics. It covers the critical `allowed`/`upgrade` handling but does not explicitly describe the full response shape or potential error conditions. For a simple two-parameter tool, this is nearly complete.

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 input schema already provides 100% parameter coverage, including an example for skill_id and allowed values for capability. The tool description itself does not add parameter-level detail, so a baseline of 3 is appropriate.

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 verb and resource: 'Reserve ONE run of a LemMeBuyIt skill against your plan's daily limit.' This clearly distinguishes it from sibling tools, which are retail/price/promotion queries and do not perform quota reservations.

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 gives explicit usage guidance: 'Call this exactly once at the start of a skill.' It also provides precise conditional behavior: if `allowed` is false, stop and show the upgrade message. No alternative tool competes for this purpose, so the instructions are complete.

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