Two ways in. One Atlas.

REST and MCP are access methods for the same governed platform, not competing products. Identity, entitlement and scope are enforced in the same place whichever you choose. What differs is who drives the call, and which Atlas operations each method exposes today.

Which one

Choose	When
REST	Your code decides what to call. Backends, jobs, webhooks, CI, server-rendered apps. You want explicit requests, explicit responses and a schema you can generate a client from.
MCP	A model decides what to call. Coding agents, assistants, IDE integrations. You want the client to discover authorized tools and invoke them inside a session.

Using both is normal: a service writes evidence over REST while a developer agent recalls it over MCP. They read and write the same scoped memory, so neither is a cache of the other.

Where each operation lives

This is the correspondence as it exists today, not an aspiration. Where one side is empty, that capability is genuinely unavailable through that method.

Atlas capability	MCP tool	REST
Recall scoped memory	`memory_recall`	No direct operation. Recall happens inside governed chat (`POST /api/chat/stream`), which returns a grounded answer rather than the evidence rows.
Record durable memory	`memory_store`	No direct operation. `POST /api/documents/ingest` records document evidence; chat records within the governed flow.
Review recent memory	`memory_recent`	Not exposed.
Consolidate memories	`memory_consolidate`	Not exposed.
Durability checkpoint	`memory_persist`	Not exposed.
Author a behavioural rule	`rule_add`	Not exposed. The former `/api/rules` placeholders were removed on 2026-11-10; they answered `405`.
List behavioural rules	`rules_list`	Not exposed.

No parity claim. MCP is the richer Atlas surface today: explicit recall, store, consolidation, checkpoints and rules. REST reaches Atlas through governed chat and document ingestion, which is the right shape for application traffic but is not a memory API. Build on what the table says, not on symmetry.

Two different things are called MCP

The name is overloaded in this platform, and conflating them will waste your time.

	Hosted Eventium MCP	REST MCP tool routes
Where	`https://mcp.eventium.ai/mcp`	`/api/mcp/tools*` on the API
What	The governed Atlas memory tools listed above, over the Model Context Protocol.	An HTTP convenience lane over the embedded tool-template platform. Not protocol discovery.
Catalogue	Authoritative: mcp.eventium.ai.	Reads the installable tool table, which is empty in production. An empty list is an accurate answer, not an error.

If you are configuring a client, you want the hosted MCP endpoint: MCP client setup.

Authorization is the same decision

Both methods resolve the same identity, entitlement, role, project membership and permitted-operation checks server-side. The differences are in how the credential arrives and what it is allowed to drive.

	REST	MCP
Credential	`X-Api-Key`, or a signed-in browser session.	`Authorization: Bearer`, or a verified user session for interactive clients.
Scope source	The credential and the request path.	Trusted transport and session context — never a model argument.
Discovery	The published schema, identical for everyone.	Per-credential: `tools/list` returns what you are authorized for.
Status today	Live. Keys issue from the console and work.	Endpoint live; the third-party API-key lane is not currently authorized, so registered keys are refused for MCP.

Sandbox credentials are deliberately bounded on both sides: no internal billing bypass, no administrative permissions, and no standing MCP privileges. A sandbox key is for trying REST, not for acquiring tool access.

What it costs

One rate card prices Atlas work regardless of how the request arrived. Recall is charged per authorized Bank searched, writes by payload size, reads by returned size; failures, throttles and usage reads are free. The full card is in Plans and usage.

The AAU meter is implemented and live on the REST Atlas API-key path. External MCP invocations are not metered yet, because the external MCP lane is not authorized yet — read that as sequencing, not as a free tier. Nothing is purchasable and no customer is charged on either method today; allowances are the proposed commercial model.

A single journey

Create a credential in the API keys console. Read Authentication first if the session-versus-key distinction is new.
Call GET /api/me/capabilities. It reports what your credential may actually do, which beats discovering it one 403 at a time.
Pick a method from the table above. For REST, try the operation in the Playground against the live schema. For MCP, configure a client and run tools/list.
Check what it consumed: GET /api/commercial/atlas-api/usage is free and reports plan, allowance, usage and remaining balance.
When something fails, branch on the error code, not the prose: Errors and retries and Troubleshooting.

Where each thing is documented

Three domains, one job each. If two pages ever disagree, the owner below is correct.

Surface	Owns
developer.eventium.ai/docs	Onboarding, concepts, guides, plans and AAU accounting, integration choices, troubleshooting. This page.
api.eventium.ai	Endpoint definitions, schemas, request and response shapes, scopes and status codes. Generated from the running service, so it cannot drift from it.
mcp.eventium.ai	Tool definitions, the discovery and invocation contract, and service readiness.

API surface
Which operations are a developer contract.MCP client setup
Configuration for real clients.