Warrant

Developer authorization infrastructure providing relationship-based (ReBAC) and attribute-based (ABAC) access control with a hosted API and open-source self-hosted option.

Evaluated Mar 07, 2026 (0d ago) vcurrent
Homepage ↗ Repo ↗ Developer Tools authorization ReBAC ABAC RBAC fine-grained open-source Zanzibar
⚙ Agent Friendliness
60
/ 100
Can an agent use this?
🔒 Security
87
/ 100
Is it safe for agents?
⚡ Reliability
78
/ 100
Does it work consistently?

Score Breakdown

⚙ Agent Friendliness

MCP Quality
--
Documentation
82
Error Messages
80
Auth Simplicity
85
Rate Limits
70

🔒 Security

TLS Enforcement
100
Auth Strength
83
Scope Granularity
84
Dep. Hygiene
82
Secret Handling
84

Cloud-hosted API stores relationship tuples; data residency currently US-only. Open-source self-hosted option allows full data sovereignty. SOC2 in progress as of last check.

⚡ Reliability

Uptime/SLA
80
Version Stability
78
Breaking Changes
76
Error Recovery
80
AF Security Reliability

Best When

You need Google Zanzibar-style relationship-based access control with a developer-friendly API and optional self-hosting, especially for document-sharing or multi-tenant collaboration features.

Avoid When

Your team lacks the bandwidth to model a relationship graph upfront — the ReBAC model requires careful object type and relation design before it becomes useful.

Use Cases

  • Store and query object relationship graphs to implement Google Zanzibar-style permission checks (user → group → resource)
  • Check whether an agent or user has a specific permission on a resource in real time before executing an action
  • Manage fine-grained per-resource permissions for SaaS features like document sharing, workspace membership, and API key scoping
  • Build a pre-made authorization UI for users to manage their own sharing and access settings using Warrant's hosted UI components
  • Implement feature flags and entitlement checks tied to user roles or subscription tiers

Not For

  • Authentication or session management — Warrant is an authorization layer only, not an identity provider
  • Teams that require fully on-premises deployment with no internet access (self-hosted option exists but is less mature than the cloud offering)
  • Coarse-grained role systems that only need two or three global roles — this is over-engineering for simple cases

Interface

REST API
Yes
GraphQL
No
gRPC
No
MCP Server
No
SDK
Yes
Webhooks
Yes

Authentication

Methods: api_key
OAuth: No Scopes: Yes

API key passed as Bearer token. Separate keys for server-side and client-side usage. Client keys are intentionally limited in scope.

Pricing

Model: freemium
Free tier: Yes
Requires CC: No

Free tier is usable for development and small production workloads. Self-hosted version (open-source) is free with no limits.

Agent Metadata

Pagination
cursor
Idempotent
Partial
Retry Guidance
Not documented

Known Gotchas

  • Relationship checks traverse the entire warrant graph, so deeply nested groups can cause unexpectedly high latency on complex queries
  • Object types and relations must be defined in the schema before warrants referencing them can be created — schema-first design is required
  • The API does not return the reason a check was denied; agents that need to surface 'why access was denied' must infer it from the warrant graph separately
  • Batch check endpoints exist but have a lower request limit than advertised in some SDK versions — test batch sizes in staging
  • Self-hosted Warrant requires PostgreSQL or MySQL and has additional operational complexity; the cloud API is significantly simpler to get started with

Alternatives

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Scores are editorial opinions as of 2026-03-07.

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