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

Annotations already indicate readOnlyHint=true, idempotentHint=true, and openWorldHint=false. The description adds useful behavioral detail beyond those: it searches only live/published tools, matching is case-insensitive substring on three fields, and it returns up to 20 results. This clarifies scope and result limits that annotations alone do not convey. No contradiction with annotations.

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?

The description is three sentences, each earning its place: what it searches, when to call it first, and result limit. It is front-loaded with the core action and immediately follows with search scope, then usage guidance. No filler or redundant restatement of the title.

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, read-only, idempotent search tool with an output schema, the description is highly complete. It covers the data domain, matching behavior, use-case triggers, and result cap. It doesn't explain pagination or exact output structure, but the output schema exists and the operation is intrinsically list-like, so this is sufficient.

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%: the 'query' parameter already has a clear description ('Free-text search term, e.g. a tool name, use-case, or category.'). The tool description reiterates the same idea without adding materially new information about parameter format, special syntax, or edge cases, so the 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?

The description names a specific verb ('Search') and resource ('The AI Tools Index catalog of live, published AI tools'), states match fields (tool name, tagline, category name), and specifies the search is free-text and case-insensitive. It also distinguishes from siblings by positioning this as the catalog-wide search entry point, while siblings like get_tool, list_alternatives, and list_offers serve more targeted lookups.

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 description explicitly instructs 'Call this first when a user asks to find, discover, or compare AI tools by keyword, use-case, or category', giving concrete triggers and examples. It also implies that this is the initial broad-search tool before narrowing down with siblings, even if it doesn't explicitly enumerate exclusions for each sibling.

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