engine_info

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, and the description adds valuable behavioral context: 'Response is cached for 5 minutes. Does not perform any web search.' This goes beyond the annotations and clarifies the tool's side-effect-free, cacheable behavior and its non-search nature.

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 concise and well-structured, opening with the primary purpose, followed by the return format, usage guidance, and a clarifying note about caching and non-search behavior. Every sentence contributes meaning without 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?

Given this is a simple, parameterless tool with an output schema, the description covers all necessary aspects: purpose, return shape, usage timing, caching, and exclusions. It fully prepares the agent to decide when and how to invoke the tool.

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?

The tool has zero parameters, so the schema provides full coverage. The description appropriately focuses on the returned data structure ('list of enabled engines grouped by category') rather than parameters. Baseline for 0 params is 4.

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 function: 'Get available search engines and categories from the SearXNG instance.' It specifies the resource and the nature of the output. It also distinguishes itself from sibling tools by explicitly noting it 'Does not perform any web search — use the search tool for that.'

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 guidance: 'Use this to discover what engines and categories are available before calling search with specific engines or categories filters.' This clearly indicates when to use the tool versus the search tool, making usage context unambiguous.

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