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

Annotations already declare the write nature (readOnlyHint=false), open-world lookup, idempotency and non-destructiveness, so the safety profile is covered structurally. The description adds useful context — the confirmation prerequisite and the fact that it returns year-end and filing deadlines set up. It stops short of saying what happens on an already-linked company or which fields are immutable, so remainders are modest.

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 front-loaded sentences: what it saves, when to call it, what it returns. No filler, and the directive to tell the user about deadlines is functional rather than decorative.

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, and the description compensates by stating the return (year-end and the deadlines it set up) and the instruction to report them. Preconditions, scope and post-conditions are all present for a two-parameter write tool.

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 both parameters are already documented, including the multi-company selection logic of `company`. The description only reinforces that `company_number` must be the confirmed Companies House number, which is marginal added meaning over the schema.

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?

Specific verb (save/link) plus resource (a UK Companies House or Irish CRO company), and it enumerates what data is persisted (name, number, status, address, directors, year-end, deadlines). It is clearly distinguished from lookup_company, which only finds the company.

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 an explicit precondition: call only after lookup_company found the company and the user confirmed ownership. This both names the alternative and states the gating condition, leaving nothing to inference.

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