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

With no annotations, the description carries the full disclosure burden, and it does real work: it scopes the result to unpaid invoices only, defines the bucket boundaries, specifies units as integer cents, and notes grouping per currency. It stops short of stating read-only safety or whether it aggregates across all entities with no filtering.

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, zero filler: the first sentence front-loads the payload and its exact dimensions, the second gives the use case. Everything earns its place.

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?

Despite having no output schema and no annotations, the description defines the bucket structure, units, and grouping well enough for an agent to know what comes back. Only the aging-date behavior (how 'on' reshapes buckets) and read-only nature are left unaddressed.

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% and the single 'on' parameter is fully documented in the schema (YYYY-MM-DD, default today). The description adds no extra meaning about the aging date or how buckets shift relative to it, 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?

The description names a specific artifact (aging summary across every unpaid invoice) and enumerates the exact buckets it produces, so the resource is unambiguous. It does not explicitly carve itself apart from close siblings like overdue_list or invoice_status, so the differentiation is left to inference rather than stated.

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 framing line 'the answer to "how much am I owed, and how stale is it"' implies the use case but never states when to pick this over overdue_list or invoice_status, nor any exclusions or prerequisites. Usage is implied, not guided.

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