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

Annotations already declare read-only, idempotent and non-open-world, yet the description still adds real behavior: hybrid keyword+semantic matching, prompt-injection sanitization, a hard 25-hit ceiling, per-hit field contents with nullable url, and the caveats that no total match count is returned and that `indexes_unanswered` flags timed-out indexes. This is the kind of partial-failure and result-shape information annotations cannot convey.

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 purpose then result contract, then the index taxonomy, then examples—a sensible ordering. The bulleted index lists are dense but earn their space; only the 'live counts: /api/v1/search/stats' endpoint mention and the fairly long enumeration of per-hit fields feel like marginal 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?

With no output schema, the description carries the return contract itself and does so thoroughly: hit fields, `returned`, `indexes_unanswered`, and the explicit absence of a total count. Combined with index scoping and example queries, an agent has enough to call this correctly and interpret the response, with only query-syntax detail 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 coverage is 100%, so a 3 is the floor, but the description goes beyond it by explaining what each index actually contains (iocs with actor attribution, 366 adversary profiles, daily-synced CISA KEV, OTX pulses, 1,800+ blog posts) and why the archives are opt-in. It adds no guidance on `query` syntax—no mention of phrase, boolean, or field-prefix support—and `limit` is left entirely to the 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?

Opens with a specific verb and resource ('Searches threat-intelligence records about threat actors, malware, campaigns, CVEs, breaches, vendors and indicators') and immediately bounds the scope ('no general programming or web content'). An agent can distinguish this from enrich-ioc, correlate, or check-package 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?

Explicitly states the default index set, that archive indexes are 'searched only when named', and that non-security content is out of scope, plus three worked examples showing index selection. It does not route the agent to sibling tools (e.g., when to prefer enrich-ioc or correlate over a broad search), which keeps it from a 5.

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