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

Annotations already establish idempotent=true, destructiveHint=false, openWorldHint=false, so the safety profile is largely covered. The description still adds valuable behavior beyond that: it writes vdd/impact-report.generated.md and explicitly never overwrites a hand-authored vdd/impact-report.md, which materially informs the agent about side effects on existing files. It does not discuss runtime cost or permissions, keeping it short of a 5.

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 phase label and the scope list, then behavior, then the alternative, then parameter relationships — a sensible ordering. It is dense with long enumerations and the parameter-relationship sentence is crowded, but essentially every clause carries information an agent needs.

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 no explanation; the description covers the check scope, phase ordering, the written artifact and its overwrite guarantee, the alternative tool, and the two-parameter interaction. Nothing needed to call this correctly appears to be 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%, so the baseline is 3, but the description adds genuine semantics on top: 'feature narrows the check to one spec' and artifactFiles is 'omitted when resolving against a local projectRoot', which clarifies the interaction between the two optional parameters that the schema documents only in isolation.

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 ('Validate the full chain') and enumerates exactly what is validated — traceability matrix, drift, orphans, uncovered vision goals, impact metrics, assumption checks. It also names the sibling vdd_inspect as the tool for a narrower subset, so an agent can distinguish it without opening a 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?

Gives an explicit precondition ('Run after implementation is complete') and an explicit routing rule to an alternative ('for the traceability matrix or per-feature spec metrics use vdd_inspect'). This is when/alternatives guidance in full.

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