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

Annotations cover only the safety profile (readOnly/idempotent/openWorld/non-destructive), and the description adds substantial context they cannot: the full terminal_reason taxonomy, the misreading traps for unverified_registry and unknown_kind, the registry_number/registry_is_companies_house semantics, ECCTA verification fields with an explicit warning that pending/unknown are not breaches, and the credit cost reported in chain_metadata.

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, then layered disambiguation. It is long, but nearly every sentence carries information an agent needs to interpret terminal_reason and verification fields correctly. The 'both are findings, not errors' point is stated twice, a minor redundancy.

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?

With no output schema, the description carries the full burden and does so: it describes the returned tree, per-node fields, terminal reasons, registry attribution, identity-verification semantics, and chain_metadata cost. Nothing material for correct invocation or interpretation 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 both parameters are already documented there, including the 1-10 range, default, and per-level API cost. The description adds no parameter-level detail beyond the schema, 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 specific verb and resource ('Trace the full ownership chain for a UK company by recursively following corporate entity PSCs') and explicitly positions itself beyond the immediate PSC layer, which cleanly separates it from the sibling get_psc. An agent can select it without ambiguity.

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?

Closes with concrete use cases ('KYB checks, AML screening, or any task requiring beneficial ownership beyond the immediate PSC layer'), which implicitly routes shallow-PSC lookups to get_psc. No explicit exclusions or when-not-to-use statement, so it stops short of a 5.

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