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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description still adds value by disclosing return content ('how many times it has been used') — notable because there is no output schema — and by naming the underlying API endpoint.

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?

Two tight sentences with the purpose front-loaded and the identifier constraint immediately after; the trailing API endpoint reference is mildly redundant but compact and helps agents mapping to the Tito API.

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 read-only single-resource fetch, the description covers what it does, what identifies the resource, and one piece of return content, which compensates for the absent output schema. It is slightly thin on ordering/response shape and auth prerequisites that the schema only hints at.

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%, so the schema fully documents event_slug, account_slug and discount_code_id on its own. The description only echoes 'numeric id' for the lookup key and adds no format or constraint detail beyond the schema, 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?

States a specific verb (fetch) and resource (a single discount code) and pins the lookup key to the numeric id, which distinguishes it from the list_discount_codes sibling by the word 'single'. It does not name that sibling explicitly, so it falls just short of the top mark.

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?

Usage is implied by the 'single ... by its numeric id' phrasing – use it when you already know the id rather than wanting a list – but there is no explicit when-to-use, when-not-to-use, or named alternative such as tito_list_discount_codes.

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