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.

ClassifiedCall

Validated identity shared by pricing and metering.

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.

Classification

The outcome of looking at the request headers alone.

CredentialError

Missing or ambiguous tenant credentials.

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.

RetryPolicy

Ordering required when retrying a failed export.

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.

classify_request_headers

Validate unique protocol headers before authenticating or reading a body.

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.

extract_api_key

Extract exactly one API key or Bearer credential.

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.