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

With no annotations, the description carries the full burden and does substantial work: it declares the tool stateless ('nothing stored'), discloses the response contents (decision, every reason, budget left), and notes the execution environment and per-call cost ($0.001 via x402). It omits error behavior and rate limits, keeping it below a 5.

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 core value proposition and the two required inputs are front-loaded in the first two sentences, with statelessness immediately after. The trailing attribution and production URL/pricing parenthetical is operational noise for an MCP caller, though the cost figure is arguably useful.

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 nested-object tool with no output schema, the description explains what is returned (decision, reasons, remaining budget) and what the policy governs, so an agent can compose a valid call. The remaining gap is the exact nested field naming for policy and spend, which neither schema nor description fully supplies.

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 only 50% - the policy object has no schema description at all - and the description compensates by enumerating its components: per-transaction/daily/monthly caps, approval threshold, recipient/category/network allow and block lists, and the minimum-return hurdle. It says less about the spend object beyond the schema's 'amount_usd required', and does not pin exact key names for either nested object.

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 states a specific decision resource - a spend gate that returns ALLOW, DENY or ESCALATE - and frames it as a pre-spend check, which implicitly separates it from wallet_spend (the actual spending tool). An agent can tell what it does and when it applies without opening the schema.

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 when-to-use is explicit: call it 'before your agent spends money', supplying the owner's policy plus the proposed spend. There is no explicit when-not clause or named alternative, but the pre-transaction framing is unambiguous.

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