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

Annotations declare readOnlyHint=false, openWorldHint=false, idempotentHint=false and destructiveHint=false; the description adds real context on top — the $1 charge, the signed-receipt output, and confirmation that nothing is fetched over the network, which corroborates openWorldHint=false. It also discloses the auth prerequisite (checkout caller plus verified session) and that importing the receipt is a separate explicit action. It stops short of saying whether repeat calls re-charge or whether a payment_ref makes calls idempotent, which is the main remaining behavioral unknown.

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?

Front-loading the core action plus cost and return value is good structure, and the negative scope sentence earns its place. But phrases like "checkout caller and verified fixed-order session" and "x402 HTTP rail retains its existing introductory quote policy" are unexplained jargon that an agent cannot act on. Roughly a third of the text is internal billing lore rather than invocation guidance.

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?

An output schema exists, so return values need not be described, and the cost and network-boundary disclosures are valuable for a non-read-only, 8-parameter tool. What's missing is the shape and purpose of the primary inputs (manifest, policy, sample_inputs, subject_profile_sha256) and any statement of what a rejection looks like. Complete enough to understand the transaction, incomplete for actually constructing a call.

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 description coverage is 0% across 8 parameters, so the description carries the full burden and mostly doesn't: only session_id and payment_ref get indirect meaning via "checkout caller and verified fixed-order session" and the x402/quote sentence. The required agent_id and manifest, plus policy, sample_inputs, subject_profile_sha256, and request_id, receive no explanation of format, expected structure, or effect. Nested manifest/policy objects are especially opaque since both are additionalProperties-only.

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 first sentence gives a verb and object ("Run a $1 static Security Preflight and return a signed receipt"), which conveys the core action and that it is paid and produces an artifact. However, "Security Preflight" is a product-specific term with no plain-language expansion, and the description never distinguishes this tool from siblings like scan_source, screen_injection, get_security_receipt, or describe_agent. An agent knows roughly what happens but not how it differs from the adjacent tools.

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: direct MCP calls require a checkout caller and verified fixed-order session, and the final sentence clarifies that importing the receipt elsewhere is a separate action. The negative boundary "No deployed endpoint is fetched or tested" hints at when a live scan tool would be appropriate, but no sibling is named as an alternative. This is implied usage, not explicit when/when-not routing.

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