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

Annotations already cover readOnly/idempotent/openWorld/non-destructive, so the safety bar is met structurally. The description adds genuinely useful behavior beyond that: name resolution echoed as resolved_from_name, counts returned ahead of the list, and the crucial empty-result-vs-nonexistent-company disambiguation that mirrors get_filings.

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 core action and domain definition, and every sentence carries information (scope, analogy, return fields, disambiguation). It is a single dense paragraph that runs long and could be split for scanability, but there is little outright waste.

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?

No output schema exists, and the description compensates by enumerating the returned fields (charge_number, classification/description, status enum values, dates, particulars, persons_entitled, counts). Combined with input handling and the empty-result semantics, an agent has everything needed to call and interpret it correctly.

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 baseline is 3. The description goes beyond the schema by explaining the name-resolution side effect (resolved_from_name echo) and warning against guessing a number from memory because a plausible wrong one reads as a clean empty result — behavior the schema description hints at but the tool-level text reinforces contextually.

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 specific verb+resource ('Retrieve the charges register for a UK company') and immediately defines the domain with the US UCC lien analogy, which anchors meaning for an agent unfamiliar with UK charges. It also names sibling tools (search_companies for input sourcing, get_filings for the disambiguation pattern), so it is distinguishable from the rest of the register family.

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?

Clear context: use this to pull secured-lending registrations, accept either a company_number (from search_companies) or a NAME, and it explicitly frames the no-charges vs non-existent-company case as the reason to call it. It stops short of naming a specific alternative tool or a when-not-to-use condition, so it is strong but not fully routing.

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