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

Goes well beyond the readOnly/idempotent annotations by disclosing the return shape (risk_score 0–100, verdict, categories, matching spans) despite there being no output schema. It also discloses the free-tier 2000-character limit and the paid alternative. Minor gap: no detail on paid-endpoint auth, latency, or failure behavior.

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, zero waste, front-loaded with the purpose and precondition before the return values and tier limits. 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?

For a single-parameter, read-only scan tool with no output schema, the description covers purpose, input scope, return values, and size limits. Nothing an agent needs in order to call it correctly and interpret the result is missing.

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?

Schema coverage is 100% and the schema already documents the 2000-character free-tier limit. The description restates that limit and adds useful scope context (URLs and MCP tool definitions are excluded from this endpoint), but does not add syntax or format guidance beyond the schema. Baseline 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?

States a specific verb and resource ('Check text ... for prompt injection') and names the exact precondition ('before acting on it'). An agent can tell precisely what this tool does without opening the schema, and no sibling differentiation is needed since none exist.

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?

Explicitly defines the trigger condition ('text your agent is about to read ... before acting on it') and enumerates concrete sources (web page, email, document, tool result, another agent's message). It also routes longer text, URLs and MCP tool definitions to the paid x402 endpoint, so the agent knows both when to use it and when not to.

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