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

With no annotations provided, the description carries the full burden and discharges most of it: it enumerates every terminal_reason, pre-empts two common misreadings (unverified_registry, unknown_kind) as findings rather than errors, explains company_number nullability, and warns against reporting 'pending' verification as a breach. It does not state auth/permission needs or read-only nature, and rate limiting is only hinted at via credit cost.

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 purpose is front-loaded, but the body is a dense wall of text that repeats the same idea ('Both are findings, not errors' / 'which is a finding ... and not an error or an outage'). The terminal_reason semantics earn their space, but the redundancy costs readability.

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?

There is no output schema, so the description must document the return value, and it does so thoroughly: chain_metadata, terminal_reason values, per-node fields (company_number, registry_number, verification_status group), and which node types lack verification fields. Nothing an agent needs to call or interpret this tool 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%, so both parameters are already documented, including the per-level API cost of max_depth and the zero-padding rule for company_number. The description adds no parameter-level detail beyond what the schema supplies, so the baseline 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 precise verb and resource ('Trace the full ownership chain... by recursively following corporate entity PSCs') and describes the return shape (a tree terminating in UBOs, foreign entities, or legal persons). It also separates itself from the sibling get_psc by framing the value as 'beneficial ownership beyond the immediate PSC layer'.

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 concrete context ('Use this for KYB checks, AML screening, or any task requiring beneficial ownership beyond the immediate PSC layer'), which implicitly routes agents away from get_psc for deep chains. There is no explicit when-not-to-use or cost-based exclusion beyond the chain_metadata cost note.

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