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

readOnlyHint=true already declares this is a safe read, so the description's main added value is mapping the operation to GET /businesses/{businessId}/coupons/{couponId}. It says nothing about not-found behavior, error responses, or the default business scoping that the schema hints at.

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 short sentences with the core action front-loaded and the API endpoint as supporting detail. Nothing is wasted and nothing important is buried.

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 simple two-parameter read with full schema coverage and a readOnlyHint, the definition is nearly sufficient: action, id-based lookup, and endpoint are all present. Only minor edge-case behavior (coupon not found, permission scope) is left unstated.

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% – both coupon_id and business_id are documented, including the login-default for business_id and the provenance hint from reservio_list_coupons. The description adds no semantics beyond restating the path variables, so the baseline 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 and resource ('Get one coupon by id'), and the singular 'one' implicitly distinguishes it from the plural list_coupons sibling. It does not name an alternative explicitly, so it falls short of full sibling differentiation.

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 only implied: an agent infers it should call this when it has a coupon id rather than when it needs to browse coupons. No explicit when-to-use, prerequisites, or 'use reservio_list_coupons to find ids' guidance appears in the description.

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