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

Annotations already cover the safety profile (readOnlyHint=true, destructiveHint=false, openWorldHint=false), so the description only needs to add operational context. It adds the 'active Canadian' scope and the 'verified' quality qualifier, which are useful, but says nothing about result limits, empty-result behavior, or ranking.

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?

One front-loaded sentence with no filler; the scope qualifiers and the searchable dimensions are packed in without 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?

For a single-parameter, read-only, closed-world lookup with full schema coverage and no output schema, this is nearly complete. The only shortfall is the absence of any return-shape or result-count expectation, which matters slightly more given there is no output schema.

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 the single query param is well documented with examples, so the schema does the heavy lifting. The description adds only a modest restatement that the query can target company, brand name, or category rather than an exact identifier.

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 (Search) plus a concretely scoped resource: active Canadian referral codes, verified invite links, and sign-up bonuses, with the matchable dimensions named. It differentiates itself implicitly from the list_* siblings by being a keyword search, but never names them, so it stops short of a 5.

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?

The phrase 'by company, brand name, or category' implies the lookup use case, but there is no explicit statement of when to choose this over list_all_referral_codes, list_business_referral_codes, list_featured_referral_codes, or get_referral_code. The agent must infer that free-text lookup is the differentiator.

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