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

Annotations already establish read-only, idempotent, non-destructive and open-world behavior, so the bar is lower. The description still adds genuinely useful context: the 0-100 score, per-check pass/fail/unknown outcomes with advice, and a one-hour cache TTL that tells the agent results may be stale.

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?

Three sentences with zero filler: purpose and scope first, then return shape, then the caching caveat. Every sentence carries information an agent needs and nothing is repeated from structured fields.

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 no output schema, the description correctly takes on the return-value burden by naming the score range, per-check statuses and advice. The cache TTL is disclosed. Minor gaps remain, such as what 'unknown' means operationally or expected latency for a multi-resolver scan.

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?

With a single parameter and 100% schema description coverage, the schema already documents that a URL is accepted and only the host is used. The description adds no parameter-level guidance beyond that, so the baseline of 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?

The description opens with a specific verb and resource ("Scores how well a dApp or website domain is protected against hijacking") and enumerates the exact checks performed, so an agent knows precisely what this does. It stops short of explicitly naming the narrower siblings (check_registry_lock, check_sri), though the enumerated coverage implies this is the aggregate scan.

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?

Usage is implied rather than stated: because it bundles registrar locks, DNSSEC, SRI and CSP, an agent can infer this is the broad scan versus the single-check siblings. However, there is no explicit 'use this when you want a full picture, use check_sri when you only need one check' routing, and no prerequisites are mentioned.

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