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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds one genuinely new behavioral fact — it "runs the lookup" rather than just reading a cached document, and returns "the data plus a summary" — but says nothing about latency, failure behavior for a stale or malformed id, or whether the id namespace is shared across check types.

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, front-loaded with the action and the resource, with no filler. The trailing "plus a summary" is slightly vague but still carries information rather than padding.

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 retrieval tool with annotations and no output schema, the description covers what it takes and roughly what it returns. It stops short of telling an agent how to recover when an id is invalid or whether the lookup can be slow, which are the remaining gaps an agent would want before calling.

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 description coverage is 100% and the single id parameter already carries a concrete example ("email_security_check:acme.com"). The description only reinforces provenance ("from search") and adds no format, casing, or namespacing detail beyond the schema, so the 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?

"Fetch a DNSai result document by id" states a specific verb and resource, and the parenthetical "(from search)" ties it to the sibling that produces the id. It is distinguishable from search and from the raw DNS tools (dns_lookup, whois_lookup) because it retrieves a stored result document rather than running a new query type.

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 phrase "by id (from search)" implies the workflow — call search first, then fetch — which is real guidance, but it is implied rather than stated. There is no explicit when-to-use/when-not statement or named alternative (e.g., what to do if you only have a domain and not an id).

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