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

The annotations already cover safety (readOnlyHint, idempotentHint) and openWorldHint=false, so the bar is lower. The description still adds real behavior beyond them: matching is stemming/prefix-based ("plurals and word starts match"), which tells the agent it can search loosely and need not pass exact tokens. It omits result ordering, relevance ranking, and what an empty match looks like.

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 short sentences with zero filler. The core purpose comes first and the input-syntax hint follows, with a parenthetical example that earns its space by showing both accepted query styles.

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 zero-required-parameter, read-only search tool with no output schema, the definition covers purpose and query semantics adequately, and the schema carries the lang default and limit bounds. The main gap is category – its valid values and its relationship to query are left entirely implicit, which matters because list_categories exists as a sibling.

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 only 25%: lang is documented in the schema, but query, limit, and category are bare. The description compensates well for query (free text, sentence or keyword, plural/prefix matching) but says nothing about limit or about what category accepts or how it interacts with query. With low coverage, that leaves roughly half the parameters unexplained in either place.

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 clear verb and resource: "Find fake facts by topic." That is enough for an agent to separate it from get_fact, random_fact, and list_categories without opening a schema. It stops short of naming those siblings or explicitly contrasting the lookup modes, so it lands at 4 rather than 5.

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 gives useful input guidance ("Plain words or a sentence both work", with examples like "owls" and "anything about cheese?"), so the agent knows how to phrase a query. It never says when to pick this tool over get_fact or random_fact, nor when a category filter should be used instead of a query. Usage is implied by the name and the 'by topic' phrasing rather than stated.

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