Search and fetch (SearXNG)

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

Goes well beyond the readOnly/openWorld/idempotent annotations: it discloses the return shape (search envelope with stable ref tokens plus pages[] Markdown), the partial-failure contract ('a page that fails to fetch is reported as an error entry instead of failing the call'), and a prompt-injection warning that returned web content is untrusted. These are behavioral facts an agent cannot derive from the annotations or schema.

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?

Front-loads the composite purpose, then the return shape, then the routing rule, then the safety caveat — each sentence carries distinct information with no repetition of schema or annotation 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?

For a 12-parameter tool with an output schema and full annotation coverage, the description supplies everything an agent still needs: when to prefer it over `search`, what comes back, how partial failures behave, and the untrusted-content caveat.

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%, so the schema already documents all 12 parameters; baseline is 3. The description adds marginal value by tying `fetch_top` to observable behavior (pages[] contains the top fetch_top results) and clarifying that per-page failures surface as error entries rather than exceptions.

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?

Names a specific verb chain (search + fetch) against a named backend (SearXNG) and states the composite scope: 'immediately fetch the full content of the top results in one call'. An agent can distinguish it from siblings `search`, `fetch_content`, and `deep_search` without opening any schema.

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?

Gives an explicit selection rule: 'Use it when snippets alone are not enough; use search alone when they are.' It names the alternative tool and the condition that chooses between them, which is exactly what a routing agent needs. Only minor gap is that `fetch_content` is not mentioned as an alternative for fetching a known URL.

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