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

Beyond the readOnlyHint and openWorldHint annotations, the description discloses critical behavioral traits: 'This tool NEVER decrypts sealed contents — any decryption key in the URL fragment is discarded unread; contents are only readable by opening the verify URL in a browser.' This adds significant privacy context and clarifies the tool's non-decrypting nature, which is beyond what annotations provide.

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 concise and front-loaded, starting with the core purpose. It uses three sentences to cover inputs, outputs, and a critical behavioral constraint, with no wasted words. Every sentence provides actionable information.

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 a single-parameter tool with no output schema, the description is highly complete: it enumerates all accepted input types, lists the specific return fields (existence, live status, ciphertext integrity, attestation, validity window, issuer trust context), and explains the non-decryption behavior. This fully contextualizes the tool's operation and results.

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 describes the parameter as 'A KeyHalve verify URL, QR-code text, or bare document id.' The description adds specific id prefixes (vp_…, kh_…, cb_…) and clarifies that it accepts the raw text of a QR code, enhancing the schema's coverage. With 100% schema coverage, this extra detail justifies a score above the baseline of 3.

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 clearly states the tool's function: 'Verify a KeyHalve-sealed document.' It specifies the exact verb (Verify) and resource (KeyHalve-sealed document), and lists accepted input forms. However, it does not explicitly distinguish itself from sibling tools like keyhalve_status or keyhalve_explain, so it lacks direct sibling differentiation.

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?

The description implies usage context: it is for verifying sealed documents and returns a cryptographic verdict. It explains what inputs are accepted but does not explicitly state when to use this tool versus alternatives, nor does it mention exclusions or conditions. Thus, usage is implied rather than explicitly guided.

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