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

With no annotations, the description carries full burden and discloses key behaviors: fail-closed (charge only issued if authorized), drain-safe (cumulative cap prevents multiple small charges), statelessness (caller tracks spentMicro), and that BIII does not verify JWT signatures itself. It also mentions issuing an EIP-681 payment intent. However, it does not describe side effects like charge creation outcome when unauthorized or reversibility.

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 description is a single paragraph of four sentences, each adding distinct value: purpose and checks, fail-closed/drain-safe, JWT handling, and caller responsibility. No wasted words, perfectly front-loaded with the core action. Highly concise yet informative.

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?

Given 7 parameters (2 required), no output schema, and no annotations, the description adequately explains the authorization flow and parameter roles. However, it fails to describe the return value or output format—crucial for an agent to know what the tool returns (e.g., charge ID, payment intent). Error handling and failure modes (e.g., what happens when not authorized) are implied but not explicit.

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 71%, and the description adds meaning beyond schema for multiple parameters: explains 'verified' as attestation of JWT signature, 'spendAuth' as JWT string or object with fields, 'spentMicro' as caller's running total, and gives example for 'amountUsd' ('12.50'). It clarifies that 'amountMicro' can substitute. However, 'label' and 'amountMicro' lack schema descriptions, and description only mentions amountMicro as alternative.

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 states the tool's purpose: 'SPEND AUTHORIZATION ... create a charge AND check it against what the agent's OWNER signed off'. It specifies the resource (charge/authorization) and the action (authorization with checks). The mention of 'token, recipient allow-list, per-charge max, AND the cumulative cap' distinguishes it from related tools like till_create_charge, which likely lacks these checks.

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 description explains when to use this tool: when creating a charge that must be authorized against owner-signed limits. It provides guidance on how to use it, including handling of JWT verification ('pass verified:true after checking it, or supply a spendAuth object') and caller tracking of spentMicro. While it doesn't explicitly state when not to use it versus siblings, the context is sufficient for agents to differentiate.

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