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

Annotations already cover read-only, idempotent, non-destructive, but the description adds real domain semantics: these are ledger records and LovedOne does not move money, and payment handles are contact pointers rather than credentials. That prevents an agent from treating invoice data as a payment capability — context the annotations cannot supply.

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 what is listed and what is returned, followed by two clarifying caveats. Every sentence earns its place; nothing is padded.

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 helpfully enumerates returned fields and clarifies the data's nature, but it leaves the two undocumented parameters underspecified — especially limit and any truncation/ordering behavior — which an agent needs to call it correctly.

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 0% across two parameters, so the description must compensate and largely does not. 'This agency' hints that agencyId scopes the result, but limit (1-100) — including its default and whether results are truncated — is unaddressed in both schema and description.

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 with scope: invoices this agency issued to families, and enumerates the fields returned (amounts, status, assignment). No sibling overlaps on invoices, so no differentiation is needed, but the scope nuance ('this agency') is the only narrowing signal.

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 — an agent can infer it should call this to see an agency's invoices, but there is no statement of when to prefer it over narrower lookups like get_client or when it is inappropriate. No prerequisites or pagination-triggered caveats.

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