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

With no annotations, the description carries the full behavioral burden, and it does disclose several important traits: the operation is paid (£0.49), it returns a Stripe Checkout URL rather than the data itself, and the indicators are explicitly not a due-diligence/KYB opinion. These are meaningful disclosures an agent needs. However, it omits auth requirements, whether the company number is validated, and what the agent should do after receiving the checkout URL (e.g., redeem_pack), leaving real gaps.

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 and pack contents are front-loaded, and the parenthetical enumeration is efficient shorthand. The trailing 'Soft-Offer outbound is OFF' is cryptic and arguably earns less of its place, but overall the text is compact and skimmable.

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?

For a two-parameter tool with no output schema, the description covers cost, return shape (checkout URL), and the legal disclaimer, which is reasonably complete. It nonetheless leaves an agent unsure what to do with the checkout URL or how this relates to the redeem_pack sibling, so it is adequate rather than complete.

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%, with both company_number and filing_limit fully documented in the schema, so the baseline is 3. The description adds the 'one UK company number' scope but nothing about the filing_limit semantics or format beyond what the schema already states.

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 resource (a paid data pack for one UK company number) and enumerates exactly what the pack contains: profile, officers, PSC, filings, indicators. That is far more specific than a tautology. It does not explicitly differentiate itself from new_cos_pack or redeem_pack, but the 'one UK company number' scoping and enumerated contents give an agent a clear picture of what this tool produces.

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?

There is no statement of when to use this tool versus the siblings new_cos_discover, new_cos_pack, or redeem_pack, nor any prerequisites such as account/auth state. 'Soft-Offer outbound is OFF' hints at a policy context but does not tell the agent when this tool is appropriate. Usage must be inferred entirely from the name and pack contents.

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