3tears-mcp
Shared MCP (Model Context Protocol) framework. Per-product MCP servers compose this framework instead of reimplementing stdio transport, JWT auth, error mapping, and per-tool RBAC.
What's in here
| Module | Responsibility |
|---|---|
server |
McpServer -- wraps the official mcp.server.Server. Owns tool registration, RBAC gating before handler dispatch, structured error mapping per the MCP spec. |
tool |
McpTool dataclass (name, description, input_schema, required_permission, handler) and register_tool decorator. |
http_client |
PlatformHttpClient -- typed httpx client with JWT login + refresh-on-401. Used by both MCP server tool handlers (calling /api/v1/...) and CLI scripts. One HTTP-client implementation, two transports. |
auth |
Identity dataclass + IdentityProvider Protocol + EnvVarIdentityProvider (stdio impl). Authorizer Protocol + LocalGrantAuthorizer (default impl backed by McpToolGrantCollection). |
rbac |
McpToolGrantCollection -- BaseCollection over mcp_tool_grants. Exposes the in-memory grant cache that LocalGrantAuthorizer consults. |
migrations/ |
v01_create_mcp_tool_grants -- platform-scope DDL. Consumers register via MigrationRunner.register(epoch_pkg) (same shape as threetears.epoch). |
RBAC model
Per-tool, default-deny. Each McpTool declares a required_permission string (e.g. "conversations.read", "audit.read"). On every dispatch:
- The framework calls
Authorizer.allows(identity, required_permission). LocalGrantAuthorizerchecks whether the caller's identity matches an active grant inMcpToolGrantCollectionfor the requested permission.- If denied, the framework returns a structured MCP error to the client (not a Python exception in the response body).
The configured admin identity (env-var creds in the stdio impl) is auto-granted in memory at server startup. The grant is logged but NOT written to mcp_tool_grants. This keeps the table truthful (only operator-added grants live there).
Grant changes propagate cross-pod via the mcp.rbac epoch broadcast. LocalGrantAuthorizer subscribes to Subjects.mcp_rbac_epoch() via an EpochListener; on bump it reloads the grant cache from L3. Cold-start primes from EpochClient.current(...). Missed broadcasts recover via the standard pull-on-stale path.
Identity in v1
EnvVarIdentityProvider returns one fixed Identity for the lifetime of the server, derived from env-var credentials. v2 (HTTP transport + per-call bearer-token identity) plugs in by adding a BearerTokenIdentityProvider; the rest of the framework is unchanged. The Authorizer.allows(identity, permission) interface is unchanged between v1 and v2.
Stdio transport discipline
Every byte on stdout/stderr from a stdio MCP server confuses the client. The framework configures logging to a file or to NATS; no module under threetears.mcp should write to sys.stdout / sys.stderr. An AST enforcement test guards this.
Postgres backing
CREATE TABLE IF NOT EXISTS mcp_tool_grants (
grant_id UUID PRIMARY KEY,
principal_type TEXT NOT NULL, -- 'user' | 'group' | 'role'
principal_id UUID NOT NULL,
tool_name TEXT NOT NULL,
permission TEXT NOT NULL,
date_created TIMESTAMPTZ NOT NULL DEFAULT now()
);
Mutation paths (admin POST /admin/mcp/grants, DELETE /admin/mcp/grants/{id}) bump Subjects.mcp_rbac_epoch() after the row commit; sibling pods reload via the epoch listener.
1 maintainer
Release files for 3tears-mcp 0.45.1
For a detailed explanation of source distributions (sdists) and built distributions (wheels), please see the package formats documentation.
Source distribution (sdist)
| File | Size | Uploaded | |
|---|---|---|---|
| 3tears_mcp-0.45.1.tar.gz | 56.7 kB | Details |
Built distribution (wheel)
| File | Interpreter | ABI | Platform | Reset |
|---|---|---|---|---|
| 3tears_mcp-0.45.1-py3-none-any.whl | Python 3 | none | any | Details |
Total release size: 92.5 kB
Release files / 3tears_mcp-0.45.1.tar.gz
| Download URL | 3tears_mcp-0.45.1.tar.gz |
|---|---|
| Size | 56.7 kB |
| Tags | Source |
|
SHA-256 checksum How to use checksums |
09129e64b90207ad49f897d0bb48079b4fe3163b5e888e893012448af7449143
|
|
BLAKE2b-256 checksum How to use checksums |
68cb416d573ac3417bc16f7c3c8be9b3fcd0f692c2387e78f18157698441c70d
|
| Upload date | |
|
Uploaded using Trusted Publishing? What is trusted publishing? |
Yes |
| Uploaded via |
twine/7.0.0 CPython/3.13.14
|
Provenance
Provenance describes where a file came from. On PyPI, provenance is shared via attestations, which provide a verifiable record of the build or publishing details. View details, limitations and caveats.
PyPI Publish Attestation
PyPI verified that this artifact, at this checksum, originated from the publisher listed below.
Signed by GitHub Actions, verified by PyPI on Sep 17, 2026.
Transparency logRelease files / 3tears_mcp-0.45.1-py3-none-any.whl
| Download URL | 3tears_mcp-0.45.1-py3-none-any.whl |
|---|---|
| Size | 35.8 kB |
| Tags | Python 3 |
|
SHA-256 checksum How to use checksums |
90c1f9255a31de337bc10c771c84253c6d38124932a2efbd5cea93f49cefd8f5
|
|
BLAKE2b-256 checksum How to use checksums |
76b312de478ac4dc9268fe2950a931b03b7fcaceeb2a70213f422fbd5666c56b
|
| Upload date | |
|
Uploaded using Trusted Publishing? What is trusted publishing? |
Yes |
| Uploaded via |
twine/7.0.0 CPython/3.13.14
|
Provenance
Provenance describes where a file came from. On PyPI, provenance is shared via attestations, which provide a verifiable record of the build or publishing details. View details, limitations and caveats.
PyPI Publish Attestation
PyPI verified that this artifact, at this checksum, originated from the publisher listed below.
Signed by GitHub Actions, verified by PyPI on Sep 17, 2026.
Transparency log
