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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, covering the safety profile. The description adds valuable behavioral context beyond annotations: it emphasizes 'exact title' matching, notes performance characteristics ('faster + cheaper'), and explicitly lists the returned content. This goes beyond what annotations alone provide, though it doesn't describe error handling for missing titles.

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: first states the function and performance, second lists return items, third provides usage context and a pointer to an alternative. There is zero fluff or redundancy.

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 simple, one-parameter read-only tool with a rich output schema and strong annotations, the description covers what the tool does, returns, when to use it, and how it compares to alternatives. No additional context seems necessary for an agent to select and invoke it correctly.

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% for the title parameter, so the baseline is 3. The description adds semantic nuance by emphasizing 'exact title' and 'canonical title,' clarifying the precision required. It also contextualizes the title's role in getting a 'standard prose answer.' This extra guidance justifies a score above baseline.

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 clearly states the tool's purpose: 'AUTHORITATIVE summary of a Wikipedia article by exact title' and enumerates the return values: 'lead paragraph, one-line description, thumbnail image, and a few related-content links.' It also distinguishes it from sibling tools like get_article_sections, making the purpose unambiguous.

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 provides explicit when-to-use guidance: 'Use when you already have the canonical title (got it from search_wikipedia, or it's a well-known entity) and need the standard 'what is X' prose answer.' It also names alternatives and exclusions: 'typically faster + cheaper than search_wikipedia + get_article_sections + scrape' and 'For the full section breakdown use get_article_sections.' This is exemplary usage guidance.

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