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

Annotations already carry readOnly/idempotent/non-destructive/openWorld=false, so the bar is lower, and the description still adds real signal: ranked results, facet counts, freshness provenance ('when the site was last confirmed alive'), and a separate labelled sponsored block that tells the agent ads are isolable from organic hits. It omits the 25-per-page / 400-page caps, but those live in the schema.

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 sentences, zero filler, with the core capability front-loaded and the prerequisite pointer placed last where it is needed. Every clause carries information.

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?

Output schema exists so return shape needn't be spelled out, yet the description still flags the sponsored-block separation an agent would otherwise miss. With full annotation coverage, 86% schema coverage and no required parameters, nothing an agent needs to call this correctly is absent.

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 86%, so the schema already documents page, perPage, query, pricing, category and task. The description adds little syntax detail beyond naming the search axes, though the list_taxonomy pointer usefully reinforces that category/task expect slugs rather than free text. Baseline 3 is appropriate.

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?

Specific verb + resource ('Search the NeedAnAI catalogue of 15,000+ AI tools') with the searchable axes (free text, pricing model, category, task) and catalogue scale stated up front. An agent knows immediately this is the free-text/browse entry point rather than a lookup by id (get_tool) or a comparison (compare_tools).

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 routes the agent to list_taxonomy for valid category and task slugs, which is the key prerequisite for two of the seven parameters. It does not, however, say when to prefer recommend_for_task or search_articles over this tool, so the sibling routing is only partially covered.

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