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

Annotations already provide readOnlyHint, openWorldHint, idempotentHint, and non-destructive flags; the description adds concrete context such as the free challenge returning DENY+deny_id, the exact unlock amount, and Probe's non-authorizing nature. No contradiction exists because the described POSTs are external endpoints, not the tool's own state mutations.

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 compact and every sentence contributes distinct information: primary path, challenge response behavior, unlock terms, and alternatives/probe caveat. It is front-loaded with 'PRIMARY agent buy path.' The telegraphic, jargon-heavy style slightly reduces scannability, but it avoids waste.

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?

Given the rich annotations, 100% schema coverage, and existing output schema, the description adds critical missing context: exact payment amount, duration, alternative price tiers, and probe limitations. This is sufficient for an agent to decide when and how to invoke the challenge/unlock flow. Omitted details like authentication are not essential given openWorldHint.

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 covers 100% of parameters with meaningful descriptions (sql preview, agent_id, schema_ddl). The tool description does not add significant parameter-level detail beyond the schema; it mentions the unlock amount but that is not a parameter. Baseline 3 is appropriate since the schema does the semantic heavy lifting.

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 identifies the tool as the 'PRIMARY agent buy path' and details the specific challenge/unlock protocol, including the exact $100 USDC unlock and resulting 500 PASS / 7d. It also distinguishes from Gateway invoice and Probe alternatives. However, it relies on telegraphic endpoint references rather than a clean declarative verb+resource statement, which slightly reduces clarity.

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 labels this as the primary buy path, lists an alternative Gateway invoice path with price tiers, and clarifies that Probe is free but never authorizes. This gives an agent useful selection cues relative to sibling tools. It could more directly reference sibling tool names, but the guidance is clear enough.

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