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

Annotations already declare readOnly, idempotent and non-destructive behavior, and the description adds genuinely non-obvious traits: defanged inputs are refanged before lookup with a `refanged` indicator, and matching is exact with a case-insensitive fallback. The enumeration of returned report fields is largely redundant with the existing output schema, which keeps this from a 5.

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?

Front-loaded with the core action, then matching semantics, then return shape, then the sibling pointer. Tight overall, though the list of per-IOC return fields is the one stretch that restates structured output rather than adding meaning.

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 read-only batch lookup with a full input schema and an output schema, the description covers the important unknowns: refanging, match semantics, and how misses are surfaced via `not_found`. Nothing essential to calling it correctly is missing.

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 both `values` and `max_matches_per_value` are already documented in the schema, including defanged formats and limits. The description adds no format, syntax or edge-case detail 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?

States a specific verb and resource: checking many IOCs at once against Rösti's threat-intelligence reports. It also explicitly separates itself from the single-value sibling by saying 'Use lookup_ioc for all matches of a single value,' so an agent can route correctly without opening either 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?

Gives a clear batch context ('Check many IOCs at once') and names the alternative for the single-value case. It does not address how this differs from sibling search_iocs, which is a plausible source of confusion, so it stops short of full when/when-not coverage.

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