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

With no annotations provided, the description fully discloses behavior. It states that output is Ed25519-signed raw facts (ensuring authenticity), enumerates the fact categories, and explicitly declares 'Facts only (never 'legit/scam')' to set expectations about the nature of the output. It also reveals pricing and tier, which are important operational details.

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 concise, fitting key details into three sentences. It front-loads the core purpose. However, the marketing clause 'the one check every other agent wallet skips' does not directly aid tool selection or invocation, slightly diminishing the value of that sentence.

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 tool's complexity (multiple fact types), lack of output schema, and no annotations, the description adequately explains what the agent should expect: raw facts with Ed25519 signing. It lists the specific fact categories but does not detail error cases or the exact output format, leaving minor gaps that could affect agent workflows.

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%, so the baseline is 3. The description adds meaning by linking the 'brand' parameter to brand-impersonation similarity and 'expected_price' to price-deviation observation, which clarifies the purpose of optional parameters beyond the schema's generic descriptions.

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 purpose: to obtain Ed25519-signed raw facts about a counterparty before payment. It specifies the resource (counterparty/storefront domain) and the concrete data points returned (domain registration age, TLS cert, reachability, redirects, brand similarity, price deviation). This strongly distinguishes it from sibling tools like onyx_merchant_fact_check by emphasizing pre-payment verification.

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 tells the agent when to use this tool: 'Before your agent pays a merchant.' This is clear context. However, it does not explicitly mention alternatives or when not to use it, though the line 'the one check every other agent wallet skips' implies uniqueness. It could be improved by naming sibling tools to avoid confusion.

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