Crate mcp_usage_kit 

Tower metering for rmcp Streamable HTTP servers.

This is the small public facade intended for application dependencies. It re-exports the protocol semantics, billing pipeline, and edge configuration so an application needs only one cargo add.

use std::sync::Arc;
use mcp_usage_kit::{EdgeConfig, InMemoryTenantStore, MeterLayer, Tenant};

let tenants = Arc::new(InMemoryTenantStore::new());
tenants.insert_unchecked("development-key", Tenant::new("acme", "cus_acme"));
let metered = MeterLayer::new(EdgeConfig::new(tenants)).layer(rmcp_service);

Re-exports

pub use mcp_usage_core as core;

pub use mcp_usage_export as export;

pub use mcp_usage_tower as tower;

pub use mcp_usage_store as store;

Structs

AggregatedUsage

One pre-aggregated provider event ready for export.

Billable

A charge to record against a tenant.

BillingPipeline

Coordinates a UsageBuffer with an off-path exporter.

Call

The call being priced, as known from its (trusted) headers.

CompositeExporter

Fan-out exporter for logs, billing, analytics, and audit sinks.

DeferredCompletions

Queue of terminal accounting waiting for somewhere to await.

EdgeConfig

Runtime configuration shared by every cloned metering service.

EdgeMetrics

Process-local edge counters.

FnExporter

Adapter for an application-owned async export function.

InMemoryTaskStore

Process-local task attribution for an embedded server.

InMemoryTenantStore

Mutable in-memory tenant table for development and embedded deployments.

Limits

Tenant limits. None means unbounded.

LogExporter

Stateless exporter that emits structured log events.

MeterEventDeadLetter

A meter event that needs application-owned reconciliation.

MeterEventExporter

Exports pre-aggregated usage through an application-supplied provider.

MeterEventProviderError

Sanitized batch-wide provider failure without per-event outcomes.

MeterLayer

Tower layer that installs MeterService.

MeterService

Service produced by MeterLayer.

MetricsSnapshot

Point-in-time metric values.

NoopRecorder

Shared, no-op recorder for deployments that want attribution metrics only.

OpenTelemetryMetrics

Registration guard for the OpenTelemetry observable instruments.

PriceBook

Per-name unit pricing with a fallback.

TaskAttribution

Pre-priced durable-task attribution without the original name or URI.

Tenant

Authenticated tenant configuration used by the edge.

Usage

Usage already committed in the current window.

UsageBuffer

Thread-safe in-memory aggregator with bounded idempotency memory.

UsageEvent

One delivered unit event emitted by the request path.

Enums

Charge

The verdict.

EdgeConfigError

Invalid edge configuration.

ExportError

Provider export failure.

FreeReason

Why a call was not billed. Kept specific so an operator answering “why is my bill lower than my request count” gets a real answer from the metrics.

LimitDecision

Successful reservation or the reason admission was denied.

LimitReason

Why a usage reservation was rejected.

MeterEventDeadLetterReason

Why a meter event was quarantined for reconciliation.

MeterEventOutcome

The provider’s final or retryable disposition for one meter event.

Method

A method named in the Mcp-Method header.

RecordError

Recording failures are internal synchronization failures only.

RecordOutcome

Result of attempting to record an event.

TaskOriginKind

Non-identifying method category retained for a durable task.

TaskStoreError

A sanitized durable-task store failure.

WeakApiKey

Why an API key was refused as too weak to be safe.

Constants

API_KEY_HEADER

API-key header accepted in addition to Authorization: Bearer.

METHOD_HEADER

Mirrored JSON-RPC method request header.

MIN_API_KEY_BYTES

Shortest API key accepted by validate_api_key_strength.

NAME_HEADER

Mirrored tool, prompt, or resource name request header.

PROTOCOL_VERSION_HEADER

Standard protocol-version request header.

Traits

BatchExporter

Exports a prepared batch away from the request path.

MeterEventProvider

Submits ordered batches of pre-aggregated usage to a billing provider.

TaskAttributionStore

Persists pre-priced, non-identifying attribution under a durable task ID.

TenantStore

Resolves a presented high-entropy API key without retaining its plaintext.

UsageRecorder

A synchronous usage sink suitable for the HTTP hot path.

Functions

assess_limits

Atomically assess a proposed usage increment against quota and spend caps.

decide

Decide what a completed request/response exchange is worth.

decide_with_task_attribution

Decide an exchange using pre-priced, non-identifying task attribution.

decide_with_task_origin

Decide an exchange while supplying the call that created a polled task.

hash_api_key

SHA-256 lookup hash for an API key.

install_opentelemetry

Register low-cardinality observable counters with an application-owned meter.

validate_api_key_strength

Reject API keys that are obviously too weak to be compared by digest.

Type Aliases

ExportFuture

Boxed future returned by object-safe billing exporters.

MeterBody

Response body returned by MeterService.

MeterEventProviderFuture

Boxed future returned by a meter event provider.

SharedExporter

Convenient trait-object alias for composing exporters at runtime.

SharedRecorder

Convenient trait-object alias used by the edge layer.

TaskStoreFuture

Boxed future returned by object-safe task stores.