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

Annotations already declare readOnlyHint=true, so safety is covered. The description adds genuinely non-obvious context: the absence of a template list endpoint and the origin of the id. It stops short of describing response shape or error behavior, but the added constraint is meaningful.

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: the first establishes scope and return content, the second states the constraint and endpoint. Nothing is redundant and the most decision-relevant fact is easy to find.

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 tool with no output schema, the description covers the resource, the payload contents and the id-provenance constraint. Nothing an agent needs to call this correctly is missing.

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 the baseline is 3. The description goes beyond the schema's terse 'The template id.' by telling the agent where the id physically comes from (the number in the template's URL in Vyfakturuj), which is the practical semantic an agent needs.

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 template/recurring invoice by id) and enumerates the returned payload (items, customer, schedule, settings), plus the underlying endpoint GET /template/{id}/. It also gives local-language aliases (sablona, pravidelna faktura) that help an agent match user phrasing.

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?

Explicitly explains the precondition for use: there is no list endpoint for templates, so the id must come from the user. This tells an agent not to hunt for a list tool, which is the key routing decision. It doesn't name a competing sibling explicitly, but the guidance is clear enough.

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