verify_witness

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

With no annotations, the description carries the full burden and delivers: deterministic re-computation, no LLM, behavior of `bind_sources=True`, separation of `digest_match` and `sources_match`, and the orphaned-URL case that must not be read as clean. It even explains why a moved source wants revalidation versus a changed digest wanting re-derivation.

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?

The description is dense but every sentence carries decision-relevant detail, and it is front-loaded with the primary meaning and result interpretation before the nuanced source-binding behavior and limitation. The LIMIT paragraph earns its place because it changes how a verdict should be interpreted.

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?

Given the minimal schema, no output schema, and no annotations, the description is unusually complete: it names the key return fields (`digest_match`, `stale_at_use`, `sources_match`, `sources_orphaned`), explains edge cases, and gives the fallback invocation. An agent has enough information to call this correctly and interpret the 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?

The input schema provides only a free-form `witness` object with 0% description coverage, so the description must compensate. It adds real meaning by explaining that the witness pins a store digest, may carry `bind_sources=True`, has pinned sources, and can involve a resolver, but it stops short of describing the expected witness object shape or how to obtain one.

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?

The description opens with a specific verb and resource: 'Check a hydration witness against the store as it is NOW,' and immediately defines the core result (`digest_match`). The witness-specific concepts (digest, pinned sources, stale serve) clearly separate this from sibling verify_* tools.

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 explicitly states the boundary of use: a custom resolver cannot cross the process boundary, so only local-file sources are re-read here, and non-file sources require calling `verify_witness(w, resolver=...)` in-process. This gives the agent a concrete when-to-use / when-not-to-use rule.

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