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

Beyond the annotations (idempotentHint, destructiveHint=false, readOnlyHint=false) it discloses two non-obvious traits: acknowledgement is job-blind and applies across ALL discoveries, and the call costs no credits. It also explains the no-op semantics quantitatively (contributes 0 to the returned count), though it does not say how partial failures are handled when some domains are valid and others are malformed.

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?

Four short sentences, front-loaded with purpose then constraints (scope, idempotency, cost). Every sentence carries a distinct fact an agent would otherwise have to guess.

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 single-parameter tool with annotations and an output schema, the description covers effect, scope, error tolerance, and cost. The one gap is domain string formatting, which matters given 0% schema coverage on that field.

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 0% and the only parameter is an untyped-in-prose array of strings. The description adds the intent ('company domains', passed as a list) but never specifies the expected format (bare domain vs. URL vs. with subdomain) or how many entries are practical, so it only partially compensates for the empty schema.

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-plus-resource ('Mark one or more company domains as delivered') and states the observable consequence ('so they are not returned again in future discoveries or searches'), which is what distinguishes it from find_prospects/search_prospects/get_discovery_results in the sibling list.

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 gives clear context for when this is the right call: after a domain has been acted on, to prevent rediscovery. It does not name an explicit alternative or a when-not-to-use case, but the effect statement is enough for an agent to infer the trigger condition.

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