> For the complete documentation index, see [llms.txt](https://docs.goassay.ai/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.goassay.ai/developers/zh/di-ceng-yuan-li/life-of-a-call.md).

# 一次付费调用的全过程

跟随一次付费工具调用，了解从发现、本地签名、结果检查到收款的过程。

一次付费调用有两个独立结果：智能体收到的结果，以及最终为它收取的资金。本页介绍启用付费调用并充入托管余额后，本地 `assay-mcp` 的处理流程。

## 工作原理

```mermaid
sequenceDiagram
    participant A as AI client
    participant L as Local assay-mcp
    participant S as Assay MCP server
    participant P as Provider and request verifier
    participant V as Assay result checks
    participant E as Escrow contract
    A->>L: Discover a tool and call it
    L->>S: Tool call
    S->>S: Check access, arguments and eligible providers
    S-->>L: Payment request for selected provider
    L->>L: Check guards and sign locally
    L->>S: Same call with signed payment
    S->>S: Validate payment and reserve funds
    S->>P: Mapped, signed provider request
    P->>P: Verify request before serving
    P-->>S: Result
    S->>V: Record result for checks
    S-->>L: Result and receipt, usually VERIFYING
    L-->>A: Result and receipt
    V->>V: Apply the tool's policy
    alt Refund or void
        V->>S: Release reservation, no collection
    else Settle the served call
        V->>S: Allow redemption
        S->>E: Submit signed payment
        E->>E: Move customer balance into payment hold
        alt Timely report upheld
            S->>E: Refund held payment to customer escrow
        else Hold ends without a blocking report
            S->>E: Collect held payment
            E-->>P: Provider share to payout wallet
        end
    end
```

## 一次调用的各个步骤

1. **发现工具。** 智能体读取工具列表，或搜索并阅读工具完整说明。发现结果提供输入结构和价格。URL 与智能体策略决定它能找到什么。
2. **选择提供方。** Assay 验证参数，按访问权限、提供方规则、契约兼容性和付款资格检查可用提供方。在这条付费流程中，它会提出一个提供方，但尚不调用端点。
3. **请求付款许可。** Assay 返回 `PAYMENT_REQUIRED`。请求标明提供方、金额、资产、网络、托管合约、调用身份和付款序号。对于这个未签名的报价，不会调用提供方，也不会预留资金。
4. **本地检查和签名。** `assay-mcp` 将请求与已转发调用、近期报价、内置付款配置、密钥权限和限额核对。它也会检查获准付费 URL、可选提供方限制和所需确认。然后用本地支付密钥签名，以相同幂等键重新发送同一次调用。
5. **预留资金并调用提供方。** Assay 将已签名付款与自行计算的调用核对。重试仍使用先前提出的提供方和契约版本。发出映射后的提供方请求前，先预留金额。普通提供方请求带有 Assay 请求签名；已保存的身份认证请求头会附加到其配置的源站。
6. **认证并处理。** 在签名保护配置下，提供方验证器会在处理函数运行前检查签名、请求体摘要、时间窗口和一次性随机数。提供方返回数据。Assay 对响应分类，并映射为工具承诺的结构。
7. **返回结果并检查。** 可用的映射数据结果会持久记录，供异步检查。初始收据通常为 `VERIFYING`：价格金额被暂扣，尚未最终收费。归因于提供方的输出结构违规可以立即退款。请求或系统错误会作废，不会视为数据质量失败。
8. **应用判定。** 启用执行的失败判定会释放预留，并记录提供方违规。误用的检查会使付款作废，但不记违规。允许结算的决定使已签名付款可以提交上链；合约将资金从客户余额移入付款暂扣。
9. **收款或退款。** 链上暂扣通常从兑付起持续一小时。符合条件的客户问题报告尚未关闭时，Assay 会等待收款；报告被认定成立且暂扣付款仍可退款时，会退款。否则，收款会支付提供方份额和平台费。请使用收据上的提交截止时间：保证可提交报告的窗口在允许收款之前结束。

## 影响集成的细节

| 情况                    | 含义                                  |
| --------------------- | ----------------------------------- |
| 检查期间已收到结果             | 你已获得数据，但最终收费尚未确定。请阅读收据状态。           |
| 已提供服务的调用标记为 `SETTLED` | 服务判定已完成。链上兑付和提供方收款仍可能待处理。           |
| 付款签名窗口到期前未能收款         | 已提供服务的调用可能成为欠款。结清前暂停付费调用；免费调用仍可使用。  |
| 网络超时                  | 不能证明提供方是否运行，也不能证明是否付款。请复用该逻辑操作的幂等键。 |
| 签名重试时提供方已不再合格         | Assay 会拒绝这笔付款，不会悄悄改为向其他提供方付款。       |

图中展示的是向签名保护提供方发出的已签名付费调用。免费调用和仅使用 API 密钥的端点采用不同流程。付款设置见[付费流程](/developers/zh/shi-yong-gong-ju-ru-men/how-paying-works.md)，不确定结果的处理见[重试与幂等](/developers/zh/shi-yong-gong-ju-jin-jie/retries-and-idempotency.md)，提供方身份认证见 [API 密钥还是签名](/developers/zh/shang-jia-ni-de-api-ru-men/api-key-or-signature.md)。

## 延伸阅读

* [访问策略](/developers/zh/shi-yong-gong-ju-jin-jie/access-policy.md)
* [支出限额](/developers/zh/shi-yong-gong-ju-ru-men/spending-limits.md)

## 下一步

* [调用如何被验证](/developers/zh/di-ceng-yuan-li/verification.md)


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