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

Annotations already cover the safety profile (readOnlyHint, openWorldHint). The description adds genuinely new behavioral context beyond them: the exact enrichment returned (CVSS, EPSS, CISA KEV) and, notably, the per-call pricing model ($0.003 USDC via x402 or prepaid credits, free trial), which is material to invocation decisions.

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-loaded with the core purpose and efficiently packaged as two mode clauses plus a pricing sentence. The first sentence is dense and run-on, but every clause carries information; no filler.

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?

With an output schema present, return structure need not be explained, and annotations cover safety. The description still supplies mode semantics, enrichment fields, and pricing, leaving it complete enough for correct invocation; only sibling routing is unaddressed.

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 goes beyond the schema by establishing the disjoint usage contract between 'id' and 'package/version/ecosystem' (mutually exclusive modes) and supplying concrete examples (CVE-2021-44228, lodash, npm) that the schema does not state.

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+resource ('Vulnerability lookup') and enumerates two concrete modes (by id, by package) with supported ID formats, so the agent knows exactly what it returns. It does not differentiate from adjacent siblings like package-audit, package-check, or dependency-report, so it stops short of a 5.

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?

It clarifies the two usage patterns (lookup by id vs. list-by-package with optional version), which is useful implied guidance. But it never says when to prefer this over similarly-scoped siblings (package-audit, dependency-verdict, package-check), so routing guidance remains incomplete.

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