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 adds the upstream endpoint and the response envelope shape ({ meta, response }), which is real context, but it says nothing about auth requirements, rate limits, or what meta contains (total counts, next-page cursors), so the added behavioral depth is modest.

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?

Three short sentences, front-loaded with the purpose, then the endpoint, then the parameter/return facts. No filler. It could be slightly tighter by not repeating the parameter list already in the schema, but it wastes little space.

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, the description carries the burden of describing returns and does so only as '{ meta, response }' without explaining meta's pagination/count fields. Combined with zero usage routing against get_invoice, it is adequate but leaves the agent to discover envelope details empirically.

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 every parameter is already fully documented in the schema (including defaults, ranges, and the _filters mini-grammar). The description merely restates the parameter family names (_page/_limit/_fields/_filters/_search), adding no syntax or semantics beyond the schema — baseline 3 is appropriate.

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+resource ('List invoices') and pins it to the concrete upstream endpoint GET /api/v0/invoices, so the agent knows it is a list operation over the invoices collection. It does not explicitly distinguish itself from the singular sibling get_invoice, which is the main remaining ambiguity.

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: the mention of _filters/_search/_page hints at what this tool is good for (paged, filtered, searched enumeration), but there is no explicit when-to-use guidance and no mention of get_invoice as the single-record alternative. An agent can infer the division of labor from the name but not from the text.

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