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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, yet the description still adds substantial behavior: the tool returns only result IDs rather than records, per-register success is reported via registers_searched/registers_unavailable with is_partial derived from it, empty results are ambiguous rather than negative, and total register failure raises instead of returning empty. This is exactly the kind of failure-mode context annotations cannot carry.

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-loaded with the one-line purpose, then the sources, then the result-ID contract, then the partial-failure semantics. Every sentence carries information an agent would otherwise get wrong, and nothing is repeated from the schema or annotations.

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?

An output schema exists so return values need not be spelled out, but the description still supplies the workflow-critical detail that outputs are IDs requiring a follow-up fetch and how to read partial results. For a one-parameter, open-world aggregation search, nothing needed to call or interpret it correctly is missing.

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% and there is a single parameter whose accepted input types (company, charity, director name, keyword) are already documented in the schema. The description adds no further syntax or format guidance beyond that, so the baseline of 3 applies.

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?

States a concrete verb and resource (search across all UK due diligence registers simultaneously) and enumerates the underlying sources: Companies House, Charity Commission, disqualified directors, Gazette insolvency. The word 'simultaneously' plus that enumeration implicitly separates it from the per-register siblings like dd_company_search and dd_charity_search, so an agent can tell it is the aggregating entry point.

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 explicit downstream guidance: 'use fetch with each ID to retrieve the full record', which pins the correct next step. It also sets an interpretation rule for ambiguous results (empty ids + is_partial = unresolved). It does not explicitly say when to prefer a targeted sibling over this broad search, which keeps it below 5.

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