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

Annotations already set readOnlyHint=true, idempotentHint=true, destructiveHint=false, lower the bar. The description adds genuine context: it names the underlying engine (Mk4 Zig-WASM) and, critically, defines the success threshold ('true if mission-ready >= 100'), which tells the agent what a positive result means. It stops short of describing failure mode on malformed YAML (throw vs. false), but the added value is meaningful.

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?

Two short sentences, zero redundancy. The first sentence states the operation and engine; the second states the return semantics with the exact threshold. Every phrase earns its place.

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?

For a single-parameter, read-only, idempotent tool with a well-described return condition, this is nearly complete. The only gap is the failure mode for syntactically invalid YAML when the engine score is undefined. An agent can call and interpret results correctly with what's given.

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% — the schema fully describes 'content' as the raw .faf YAML content. The description reinforces that it's YAML and adds the engine/threshold context, but adds no per-parameter semantics beyond that. 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 ('validate') with a specific resource ('.faf YAML content') and clarifies the engine used. It adds meaning by defining what 'valid' means — mission-ready, score >= 100 — which goes beyond the tool name and title. It doesn't explicitly contrast with sibling tools like faf_analyze, so it's not fully demarcated.

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?

No guidance on when to use validation over analysis (faf_analyze), delta checks, or the various search/query siblings. The description tells how the tool behaves but gives the agent no explicit selection criteria, and no mention of when not to use it.

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