Documentation
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Overview ¶
Package client pays for MCP tool calls made with the official MCP Go SDK (github.com/modelcontextprotocol/go-sdk), matching mppx's McpClient.wrap.
Wrap installs sending middleware on an *mcp.Client, so every session it connects, and every CallTool on them, handles payment challenges whether they arrive as payment-required JSON-RPC errors (-32042 or -32043) or as tool results carrying _meta["org.paymentauth/payment-required"]. The client pays with a configured method and retries the call with the Credential in _meta["org.paymentauth/credential"]; Receipt reads the receipt from the result:
c := mcp.NewClient(&mcp.Implementation{Name: "my-client", Version: "1.0.0"}, nil)
mcpclient.Wrap(c, mcpclient.Config{Methods: []client.Method{method}})
session, err := c.Connect(ctx, transport, nil)
...
result, err := session.CallTool(ctx, &mcp.CallToolParams{Name: "premium_tool"})
receipt, err := mcpclient.Receipt(result)
Middleware returns the same handling as sending middleware to install yourself, without Wrap's per-client registry:
c.AddSendingMiddleware(mcpclient.Middleware(mcpclient.Config{Methods: methods}))
Index ¶
- Variables
- func IsPaymentRequiredError(err error) bool
- func Middleware(config Config) mcp.Middleware
- func Receipt(result *mcp.CallToolResult) (*mpp.MCPReceipt, error)
- func WithOnPaymentRequired(ctx context.Context, fn OnPaymentRequired) context.Context
- func Wrap(c *mcp.Client, config Config) *mcp.Client
- type Config
- type OnPaymentRequired
- type OrderChallenges
Constants ¶
This section is empty.
Variables ¶
var ErrPaymentDeclined = mppclient.ErrPaymentDeclined
ErrPaymentDeclined is returned, wrapped, when the approval hook declines a payment. It is client.ErrPaymentDeclined, which the HTTP client returns when an OnChallenge hook declines, so errors.Is matches either.
Functions ¶
func IsPaymentRequiredError ¶
IsPaymentRequiredError reports whether err is an MCP payment-required or payment-verification-failed error that carries at least one Challenge.
func Middleware ¶ added in v0.6.0
func Middleware(config Config) mcp.Middleware
Middleware returns sending middleware that pays for tool calls, to install with c.AddSendingMiddleware(mcpclient.Middleware(config)). It is the explicit form of Wrap: every session of c, connected before or after, uses it, and installing it again adds a second payment layer rather than replacing the first.
func Receipt ¶
func Receipt(result *mcp.CallToolResult) (*mpp.MCPReceipt, error)
Receipt returns the payment receipt in a tool result's _meta["org.paymentauth/receipt"], or nil when it has none.
func WithOnPaymentRequired ¶
func WithOnPaymentRequired(ctx context.Context, fn OnPaymentRequired) context.Context
WithOnPaymentRequired returns a context whose tool calls use fn instead of Config.OnPaymentRequired. A nil fn pays without asking.
func Wrap ¶
Wrap adds automatic payment handling to tool calls made through sessions of c and returns c. Sessions connected before and after Wrap both use it. Calling Wrap again on the same client replaces its payment configuration. Middleware installs the same handling without Wrap's per-client registry.
Types ¶
type Config ¶
type Config struct {
// Methods are the payment methods the client can pay with.
Methods []mppclient.Method
// OnPaymentRequired, when set, approves every payment before it is made.
OnPaymentRequired OnPaymentRequired
// OrderChallenges, when set, filters and sorts payable Challenges.
OrderChallenges OrderChallenges
// PaymentPreferences ranks Challenges by "method/intent" q-values.
PaymentPreferences mppclient.PaymentPreferences
}
Config configures payment handling for an MCP client.
type OnPaymentRequired ¶
OnPaymentRequired approves a payment before a Credential is created for challenge. Returning false declines it.
type OrderChallenges ¶
type OrderChallenges func( ctx context.Context, candidates []mppclient.ChallengeCandidate, ) ([]mppclient.ChallengeCandidate, error)
OrderChallenges filters and sorts the payable Challenges before one is paid; the first one returned that passes the realm checks is paid. It has the semantics and signature of client.OrderChallenges, which the HTTP client takes with client.WithOrderChallenges, so one hook converts to either: mcpclient.OrderChallenges(fn).
Source Files