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

The readOnlyHint annotation already establishes this as a safe read. The description goes beyond it by disclosing what the response contains (line items, modifiers, discounts, taxes, payments) and mapping to the underlying API call, which is meaningful since no output schema exists. It omits not-found/error behavior.

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 carrying purpose, identifier, return contents, and endpoint mapping with zero filler. Nothing could be removed without losing information.

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?

With no output schema, describing the returned contents is the right move and it is done well; the single required parameter and read-only nature are covered. Only error/not-found behavior is left implicit, a minor gap for a simple getter.

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 parameter is documented in the schema. The description's example format ('2-1008') merely repeats what the schema already states, so it adds no meaning beyond the structured data.

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 ('Fetch a single receipt') and scopes it with 'by its receipt number', which cleanly distinguishes it from the sibling loyverse_list_receipts. An agent can select it without opening the schema.

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 'single receipt by its receipt number', which tells the agent this is the lookup path when a receipt number is known, but no alternative is named and no exclusions (e.g. use loyverse_list_receipts when the number is unknown) are given.

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