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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds substantial behavioral context well beyond them: the 100-receipt-per-month hard stop, the 60 requests/minute rate-limit window, spend denominated in micro-USD, and the fact that by_key is refused with 403 owner_required and never granted to a tsk_ key. That is exactly the extra operational context an agent needs before calling.

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?

Dense but front-loaded: the core purpose and the (GET /usage) anchor come first, then the enumerated contents, then parameter behavior. It is a single long paragraph that could be split for scanning, but every clause carries information and there is no filler.

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 compensates by naming the returned quantities (used, allowance, hard_stop) and the units (micro-USD), and it covers both parameters plus the auth/refusal behavior. Nothing essential to calling this tool correctly is missing.

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 the baseline is 3, but the description adds meaning on top: it explains the by_key breakdown is per dispatch-scoped API key and gated by owner privilege (with the 403/task-key refusal), and clarifies the YYYY-MM semantics of period. It goes modestly beyond the schema text rather than merely restating it.

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 ('Read your organization's usage and quota snapshot for a billing period (GET /usage)') and then enumerates exactly what the snapshot contains: SMS/email/AI counts, the 100-receipt hard stop, the rate-limit window, and coordination-cycle spend. This is far more specific than a generic 'get usage' and implicitly separates it from broader siblings like tascan_org_analytics.

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?

It describes conditions attached to a parameter ('by_key ... owner admin session only') and the default period behavior, which implies the intended usage context. However, it never explicitly states when to reach for this tool versus alternatives such as tascan_org_analytics or tascan_get_cycle_report, leaving the choice to inference.

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