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API key management covers the complete lifecycle of an API key: creation, storage, distribution, use, monitoring, rotation, revocation, and deletion. An MCP server may use API keys to authenticate to an upstream service or, in some private deployments, to identify callers. Because API keys are bearer secrets, anyone who obtains a valid key can usually use it. Apply the official MCP security best practices at every credential boundary.
Do not rely only on static API keys to protect sensitive, critical, or high-value public capabilities. Prefer short-lived, scoped OAuth access tokens or workload identity when available.

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Identify what each key protects

Do not treat every secret as the same credential. Never forward a credential to a service for which it was not issued.

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Prefer stronger credential options

Choose the strongest option the upstream system supports:
  1. Workload identity or managed service identity
  2. Short-lived, scoped OAuth token
  3. Short-lived generated credential
  4. Rotatable static API key
Static keys are sometimes unavoidable. Limit their scope and lifetime as much as the provider allows.

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Generate strong keys

If you issue API keys:
  • Use a cryptographically secure random generator.
  • Generate enough entropy to resist guessing.
  • Add a non-secret prefix that identifies the environment or key type.
  • Show the full secret only once.
  • Store only a secure hash when the server needs to verify, but not reuse, the key.
  • Give each key a unique identifier for rotation and audit.
Do not build keys from usernames, timestamps, sequential IDs, or other predictable values.

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Store keys safely

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Production

Prefer:
  • A cloud secret manager
  • A dedicated vault
  • A hardware-backed key service
  • Workload identity that avoids stored keys
Grant the server permission to retrieve only the secrets it needs.

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Local development

Environment variables or a client credential store can be acceptable when access is restricted. Do not commit .env files. Keep them out of logs, crash reports, shell history, and shared screenshots.

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Avoid

  • Source code
  • Git history
  • Container images
  • Public client configuration
  • Database rows in plaintext
  • Tool descriptions or prompt templates
  • Command-line arguments visible to other processes
  • URLs and query strings

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Scope keys narrowly

Use a separate key for each:
  • Environment
  • Application or MCP server
  • External provider
  • Team or workload when practical
  • Permission level
Do not reuse a production key in development or staging. If the provider supports restrictions, limit:
  • Allowed operations
  • Resources or accounts
  • Source networks
  • Domains or applications
  • Usage volume
  • Expiration date

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Keep keys away from the model

The model should not need to see an API key. The MCP server or host should attach credentials after the model creates a structured tool request.
Never return a key in tool output, resource content, an error message, or a sampling request.

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Rotate API keys safely

A safe rotation avoids downtime:
  1. Create a new key.
  2. Store it in the secret manager.
  3. Allow the application to accept or use both keys temporarily.
  4. Deploy the new configuration.
  5. Verify successful traffic with the new key.
  6. Revoke the old key.
  7. Remove the old value from all stores.
  8. Record the rotation event.
Rotate immediately after suspected exposure, employee or vendor access changes, or a compromise of the system that stored the key. Scheduled rotation can reduce long-lived exposure, but automation and tested revocation matter more than changing a secret without verifying the rollout.

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Monitor key usage

Track:
  • Key identifier, never the full key
  • Timestamp
  • Calling service
  • Target API or operation
  • Success or failure
  • Source network when appropriate
  • Rate and volume anomalies
Alert on:
  • Use from an unexpected environment
  • Sudden traffic spikes
  • Repeated authorization failures
  • Access to unusual endpoints
  • Use of a retired key
  • Changes to secret-manager permissions
Make logs useful for investigation without recording the credential.

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Redact secrets from logs

Redact:
  • Authorization headers
  • API-key headers
  • Cookies
  • Query parameters that may contain credentials
  • Environment dumps
  • Request and response payload fields marked as secrets
Use allowlisted logging fields instead of recording complete headers or objects and trying to remove secrets afterward. 0mcp activity logs are designed not to store authorization headers, bearer tokens, API keys, request bodies, or response bodies. Read Logs for details.

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Respond to a leaked key

If a key may be exposed:
  1. Revoke or disable it immediately.
  2. Issue a replacement with minimum scope.
  3. Search source control, CI logs, chat, tickets, and telemetry for exposure.
  4. Review usage records for unauthorized activity.
  5. Rotate related credentials if the affected system was compromised.
  6. Remove cached copies and update deployments.
  7. Document the incident and preventive changes.
Do not wait for proof of misuse before revoking a leaked key.

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Incoming API keys

If your MCP server accepts API keys from callers:
  • Transmit them only over HTTPS.
  • Require a header, not a query parameter.
  • Store a keyed hash rather than plaintext when possible.
  • Compare values using constant-time logic.
  • Associate each key with an owner and policy.
  • Support expiration and revocation.
  • Apply per-key rate limits.
  • Avoid exposing whether a specific key identifier exists.
For public remote MCP servers, use the standard MCP authorization flow when possible.

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Upstream API keys in 0mcp

0mcp can forward an API key that the MCP client provides for your upstream API. The key is placed according to the authentication configuration for the selected source:
  • An OpenAPI 3.x or Swagger 2.0 security scheme
  • A directly configured REST API
  • A GraphQL API
Use the secure gateway header when an upstream API requires a query key. Do not place the key directly in the MCP endpoint URL. Read the 0mcp authentication model and authentication troubleshooting.

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API key checklist

  • Every key has one documented purpose
  • Production keys use a secret manager or workload identity
  • Keys are separate by environment and service
  • Permissions follow least privilege
  • Keys never enter model context
  • Logs redact credentials
  • Rotation is automated and tested
  • Revocation is immediate and documented
  • Usage is monitored by key identifier
  • Leak response has been rehearsed

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Key takeaway

A well-managed API key is narrowly scoped, securely stored, invisible to the model, monitored by identifier, easy to rotate, and immediately revocable.