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

readOnlyHint=true already tells the agent this is a safe read; the description reinforces it by naming the GET endpoint. It adds the useful detail that paid status is returned, but says nothing about pagination behavior, result volume, or total counts, so it adds only modest value beyond annotations.

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, front-loaded with the purpose. The trailing endpoint path is of marginal use to an agent but costs almost nothing, so overall it is tight and waste-free.

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 read-only list tool with full schema coverage, this is minimally adequate. With no output schema, the description should say more about what an invoice record contains or how results are ordered, which it does not.

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 page, per_page, and search_string are already documented in the schema. The description contributes nothing additional about parameter behavior (e.g., which fields search_string covers beyond 'record fields'), 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 ('List invoices') plus the notable payload attribute ('with their paid status'), which distinguishes it from the mutation sibling limoexpress_mark_invoice_as_paid. It does not explicitly distinguish itself from other list_* siblings, but the resource is unambiguous.

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?

There is no guidance on when to call this versus alternatives, no mention of preconditions (e.g., paging through results, or using it to find an invoice before calling limoexpress_mark_invoice_as_paid). Usage is only inferable from the tool name.

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