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

Annotations already declare the safe read profile (readOnly, idempotent, non-destructive, openWorld), so the bar is lower. The description still adds genuinely useful behavior the annotations cannot convey: for npm/PyPI, a nonexistent package yields found: false and vulnerable: null rather than a clean result, which prevents a false negative reading.

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?

Three tight sentences, front-loaded with purpose and capped by an explicit alternative. The ecosystem enumeration is mildly redundant with the schema's own ecosystem description, which is the only wasted verbiage.

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?

There is no output schema, so the description usefully surfaces part of the return contract (found/vulnerable on missing packages). With annotations handling safety and the schema handling inputs, this is nearly complete; the only gap is that it never sketches the shape of a positive result.

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 100%, so all three parameters are already documented in the schema. The description only restates the ecosystem list and the optionality of version ('optionally a specific version'), adding no syntax, format, or naming-convention detail beyond structured fields. Baseline 3 applies.

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 (checks) plus resource (a package/version) against a named backend (OSV.dev), and enumerates the supported ecosystems. It also distinguishes itself from the sibling supply_chain_check by naming it, so an agent can route without opening either schema.

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 closing sentence gives an explicit alternative and the condition that selects it ('Use supply_chain_check for a combined verdict'). It stops short of stating when not to use this tool (e.g., typosquatting concerns belong to typosquat_check), so it is clear but not exhaustive.

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