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 endpoint and confirms optional filtering, but says nothing about pagination defaults, result caps (only implied via the schema's top description), or ordering/sorting behavior for a list endpoint with 11 filters.

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 sentences, front-loaded with the core action and its optional filters, then the endpoint. Every clause earns its place with no redundancy.

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 read-only list tool with 11 fully documented optional parameters and no output schema, the description adequately covers the filter surface. It is only slightly thin on pagination and default-result-size behavior, which is a minor gap given the schema handles per-parameter detail.

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 documented in the schema; the baseline is 3. The description restates filter categories at a high level but adds no date-format syntax, pagination interactions, or precedence rules beyond what the schema provides.

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 clear verb+resource ('List invoices') and enumerates the filterable dimensions (contact, event, event registration, paid/unpaid, created-date range), plus the underlying endpoint. It is distinguishable from sibling list tools like list_donations and list_payments by its explicit resource, though it never names those siblings.

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?

The phrase 'optionally for one contact, event or event registration...' implies the contexts in which the filters apply, which is useful implied usage guidance. However, there is no explicit when-to-use/when-not statement and no reference to alternative tools for related data (e.g. payments vs invoices).

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