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

Annotations provide readOnlyHint=true, so safety coverage is already present. The description adds useful behavioral context beyond that: it is a cheap cache check, it requires the caller to hash the file first, and it returns a structured result containing cached status, warrant_id, and permalink. It does not describe edge cases or failure behavior, but for a simple read-only check that is sufficient.

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 three tight sentences with no filler. The core purpose is front-loaded ('Cheap cache-check'), followed by the essential workflow note and return payload. Every sentence adds value.

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 one-parameter read-only check, the description covers what the tool does, when to call it, how to compute the input, and what it returns. The presence of an output schema means return details need not be fully spelled out, but they are included anyway, so nothing critical is 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?

The schema only defines a string named sha256 with no description, so the description carries the full burden. It specifies the exact hashing algorithm and format (sha256, lowercase hex) and explains that the hash identifies the exact document, making the parameter unambiguous.

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 predicate: whether a specific document, identified by its SHA-256 hash, has already been inspected and cached. This is distinct from verify_document, which actually performs the inspection, and from sibling tools like check_pack or check_source_overlap.

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?

Explicitly instructs the agent to call this before verify_document to avoid a redundant paid inspection, naming the sibling alternative and the condition that should trigger the call. Also tells the agent to compute the SHA-256 hash itself, which is essential for correct use.

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