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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It discloses a key constraint: 'permits paid checkout only after human or principal authorization,' which informs the agent about an approval requirement. It also states it 'Returns exact plan boundaries,' giving a sense of the output. However, it does not explicitly clarify whether the tool is read-only or mutating (e.g., whether 'permits' implies a state change), leaving some ambiguity about side effects.

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?

The description is two sentences with zero fluff. The first sentence front-loads the primary purpose and usage condition; the second sentence provides the exclusion and alternative tools. Every word earns its place, and the structure is easy to parse.

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 zero-parameter tool with no output schema and no annotations, the description is fairly complete: it covers purpose, usage timing, exclusions, and a key authorization condition. It mentions 'exact plan boundaries' but doesn't elaborate on what those boundaries might be, which is a minor gap. Still, an agent can confidently decide whether to call this tool and what to expect at a high level.

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 tool takes zero parameters, and schema description coverage is 100%. The baseline for 0 parameters is 4, and the description doesn't need to add parameter semantics because there are none. It does add context about what the tool returns, which is useful but not parameter-related. Thus, a 4 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 clearly states the tool's function: 'Use when evaluation is complete and the buyer needs the official trial-first choice among the free trial, Builder, and Agency.' It specifies the resource (plan decision), the exact choices, and what it returns ('exact plan boundaries'). It also differentiates from siblings by explicitly naming alternatives ('use audit_lead_workflow or evaluate_leadproof_fit instead'), so an agent can distinguish it without opening schemas.

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 when-to-use guidance: 'Use when evaluation is complete and the buyer needs the official trial-first choice.' It also gives when-not-to-use and alternatives: 'Do not use for workflow diagnosis; use audit_lead_workflow or evaluate_leadproof_fit instead.' This leaves no ambiguity about when the tool should be invoked versus its siblings.

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