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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false. The description adds crucial behavioral detail beyond annotations: it returns a list of result IDs (not full records) and searches in parallel across specific registers. This informs the agent that a second fetch call is required, which is essential for correct invocation. Slight gap: no mention of potential pagination or rate limits, but the provided behavior is solid.

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 two sentences long, front-loaded with the core purpose, and each sentence serves a distinct function: what it does and what the output format is. No filler or repetition of schema details, making it efficient and easy to parse.

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?

The description fully covers the essential workflow: it searches a known set of registers, returns IDs, and directs the next step (fetch). Given that an output schema exists and annotations indicate read-only behavior, nothing else is needed for an agent to select and invoke the tool correctly. The description is complete for this moderately complex multi-register search.

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?

There is only one parameter, query, and the schema description covers it with 100% clarity ('Company name, charity name, director name, or keyword to search for across all UK due diligence registers'). The tool description adds no additional meaning beyond what the schema already provides. Baseline 3 is appropriate given high schema coverage.

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 uses the specific verb 'Search' and resource 'all UK due diligence registers simultaneously', listing the four named registers. This clearly differentiates the aggregate search from sibling tools like dd_company_search or dd_charity_search which target individual registers. The scope and intent are immediately obvious.

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 explicitly states that it searches across all registers in parallel and instructs the agent to 'use fetch with each ID to retrieve the full record', providing clear follow-up usage. It does not explicitly mention when not to use this tool or name alternatives, but the context is sufficient for correct selection.

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