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

Annotations already declare read-only, idempotent, open-world, non-destructive behavior, and the description adds real context beyond that: the x402 USDC price on Base mainnet and the boundary that contents are not interpreted. It doesn't describe ordering, pagination, or what happens for an unknown company number, but the safety profile is well covered.

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?

Three sentences, front-loaded with the core action, then scope, then usage and pricing. The limit range is duplicated from the schema and the pricing sentence is a bit abrupt, but there is little wasted wording.

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 structure need not be explained, and the description covers input requirement, scope, and cost. The only real gap is how 'recent' records are ordered and whether there is pagination beyond the limit cap, which matters for a list tool capped at 100.

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%, with both company_number (pattern, example, pointer to search_company) and limit (default, 1-100 bounds) fully documented in the schema. The description's restatement of 'limit defaults to 10 and accepts 1 to 100' adds no meaning 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?

The description names a specific verb and resource ('Retrieve recent Companies House filing-history metadata') scoped to 'a known UK company', and lists the record types. The Companies House / UK qualifier implicitly separates it from get_sec_filings and get_entity_filings, but it never names those siblings directly, leaving the jurisdictional split to inference.

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?

It gives concrete use cases (corporate research, due diligence, reviewing recent changes) and an explicit exclusion ('does not semantically interpret filing contents'), plus 'for a known UK company' implies running search_company first. It stops short of routing to alternatives such as get_entity_filings for non-UK entities.

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