instant_answerDuckDuckGo Instant Answer API — definitions, entities, and quick facts. Returns a normalized answer with heading, type (abstract/answer/disambiguation), source, sourceUrl, optional image/definition, and relatedTopics, plus a meta envelope. Not a full web SERP; use web_search for that. Works with no API key.
| Name | Required | Description | Default |
|---|---|---|---|
| q | Yes | Query. |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, and destructiveHint false, covering the safety profile. The description adds valuable context beyond annotations: the normalized answer structure (heading, type, source, etc.), the meta envelope, and the keyless authentication requirement. This goes beyond what annotations alone communicate.
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, front-loaded with the tool's purpose, followed by return format and key differentiators (web_search, keyless). Every sentence contributes, with no redundant or filler content.
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?
This is a simple read-only tool with a single parameter, rich annotations, and no output schema. The description covers the essential behavioral contract (return format, query scope, keyless access) and correctly positions it against siblings. No critical gaps remain.
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% with the 'q' parameter described as 'Query.' The description does not add meaning beyond the schema; it implies the query should be for definitions/entities but does not specify syntax or example formats. Baseline 3 is appropriate when the schema fully documents the parameter.
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 identifies the tool as the DuckDuckGo Instant Answer API for definitions, entities, and quick facts, using a specific verb ('Returns') and resource. It explicitly distinguishes itself from web_search by stating 'Not a full web SERP', so it is uniquely positioned among siblings.
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?
It explicitly states the intended use case (definitions, entities, quick facts) and directly names the alternative: 'use web_search for that'. This provides clear when-to-use and when-not-to-use guidance, exceeding a vague implication.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.
Each tool has a clearly distinct purpose: fetching a specific URL, retrieving a quick fact/definition, and performing a full web search. The descriptions explicitly cross-reference one another to prevent confusion.
All names use lowercase with underscores, but the grammatical pattern varies: 'fetch_url' is verb-first while 'instant_answer' and 'web_search' are noun-phrases. Mostly consistent and readable, with minor deviations.
Three tools is a well-scoped set for a search/retrieval server. Each tool contributes a distinct capability without redundancy or bloat.
The surface covers core web retrieval: fetching a page, getting a quick answer, and running a search. Missing niche features like image search or advanced filtering, but these are not critical for the apparent purpose.