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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive, so the safety profile is covered. The description adds genuinely new behavioral context: the feed is a curated intel-gateway source and the tool degrades gracefully to an informational result when unprovisioned, which prevents the agent from misreading an empty/low-confidence answer as 'clean'.

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 short clauses, front-loaded with the core action and no filler. The parenthetical '(curated intel-gateway feed)' is the only marginally expendable fragment, but it does distinguish the data source from a generic threat feed.

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?

An output schema exists, so return-value explanation is unnecessary, and the provisioning caveat covers the main failure mode. For a single-domain, three-parameter read tool this is close to complete; only expected latency or coverage limits are unaddressed.

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%, so all three parameters (domain, format, force_refresh) are already documented in the schema, including the enum and the cache-bypass rationale. The description adds no parameter-level meaning beyond that, 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?

States a specific verb and resource ('Check a domain against BlackVeil real-time threat intelligence') and immediately scopes it against a likely-confused category ('Distinct from DNSBL checks'). An agent can tell this apart from check_rbl, check_dbl, and check_mx_reputation without opening any schema.

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 DNSBL exclusion gives a clear negative condition, and 'Operator-deploy only; degrades to info when unprovisioned' tells the agent when results will be informational rather than a real verdict. It stops short of naming the specific sibling tools (check_rbl/check_dbl) or stating positive triggers such as 'use when investigating suspected malicious reputation'.

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