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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so safety is covered. The description adds genuine domain context — the default reporting window is the month, the payload spans per-agent and per-day spend plus wallet balance, credits, reset timing, and plan-lock status — but says nothing about permissions, scoping limits, or staleness, which is the kind of behavior annotations do not carry.

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?

The main purpose is front-loaded in the first clause before the colon, and there is no filler or hedging. The trailing list of payload fields, however, partly duplicates what the output schema already declares and turns the sentence into a long run-on enumeration.

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?

The tool is simple: zero required parameters, a full-coverage schema, an output schema, and complete read-only annotations. Given that, the description supplies enough domain framing to call it correctly; the only real omission, routing guidance versus siblings, is captured under usage guidelines rather than completeness.

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?

Only one parameter, and the schema already documents it at full coverage, including that it is optional and how to obtain the id via list_companies. The description adds no syntax or semantics beyond the schema's own 'whose budget' framing, so the high-coverage baseline of 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 clearly identifies the resource being reported — monthly spend against budget broken down by agent and day, plus wallet/credits state — which is specific enough for an agent to know what data it gets. It lacks an explicit verb (it reads as a noun phrase, 'The month's spend...') and never names the related siblings it is not, such as ledger, billing_page, or plan, so differentiation is left to inference.

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?

There is no when-to-use or when-not-to-use guidance at all. With near-neighbours like ledger, billing_page, plan, plan_settings, and buy_credits in the sibling list, the description never indicates whether this is the read-only overview versus a transaction log or a plan-management tool, leaving the agent to guess.

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