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

Annotations already declare destructiveHint=true and openWorldHint=false, and the description adds concrete context beyond them: it overwrites any existing vdd/vision.md, requires a prior vdd_init, and is a run-once step. That is exactly the destructive/permission context an agent needs.

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, artifact, and file contents, then prerequisites and alternatives. It is dense but mostly earns its length; the freeform/not-a-title constraint is stated twice (in the prose and again under 'Parameter relationships'), which is mild redundancy.

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 values need no explanation; the description covers prerequisites, overwrite behavior, ordering, and the amend-vs-rerun decision. An agent has everything needed to call this correctly in the VDD workflow.

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 real meaning: statement must be freeform prose of 1-3 paragraphs and specifically not a title, and projectRoot must match the root used by vdd_init. This goes beyond the schema's terse one-line param docs.

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 precise verb and artifact ('Expand a freeform vision statement into vdd/vision.md') and enumerates exactly what the file contains (Impact Model, Stakeholder Map, Success Metrics, Constraints, Target Domains). It also names the sibling it is not (vdd_amend), so an agent can distinguish it without opening another 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 explicit sequencing ('run once, after vdd_init and before vdd_strategize') and a named alternative with the condition that selects it ('to revise a vision once downstream artifacts exist, use vdd_amend so the change cascades'). Nothing about when/when-not is left to inference.

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