Treat the config as sensitive until the token is removed. Move the credential into a vault, replace the value with a reference, and make the process resolve it only at runtime so the file itself can be shared safely.
Why MCP config files should not carry live API tokens
An MCP config is often treated like an integration artifact, but a live token turns it into a credential-bearing object. That changes how it should be handled, shared, reviewed, and stored. The right pattern is to keep the config portable while moving the secret into a dedicated secret store, so the file no longer exposes usable access if it leaks.
That separation matters because MCP setups are commonly copied across environments, checked into repos, or distributed to teammates. If the token remains inline, every copy becomes a valid secret distribution channel. By contrast, a reference-based design keeps the config readable and the credential controlled by the system that resolves it at runtime.
For teams building or operating mcp integration, MCP Security Guide is the most direct internal reference for token passthrough, local server credentials, and gateway patterns that avoid exposing secrets in the config itself.
How to make the config safe to share
The practical goal is to make the configuration declarative, not secret-bearing. Store the API token in a vault or secret manager, then replace the literal value in the MCP config with a pointer, environment reference, or other runtime-resolved handle. The config should describe where to obtain the credential, not contain the credential.
This also changes the operational lifecycle. When the token is externalised, the config can be reused without forcing a secret rotation every time the file moves. Rotation, revocation, and access review become properties of the secret store and the identity that reads it, rather than of every downstream copy of the file.
API Key Management Guide supports that lifecycle view by focusing on scoping, storage, rotation, revocation, and response when a key leaks.
Model Context Protocol: Authorization specification is useful here because it frames mcp server as resource servers and reinforces audience-bound authorization instead of token passthrough.
What good runtime resolution looks like in practice
Runtime resolution should be deterministic, bounded, and easy to audit. The application or MCP host should fetch the token only when needed, from a controlled secret source, and should avoid persisting it into logs, temp files, shell history, or developer-visible config snapshots. If the runtime cannot retrieve the secret, it should fail closed rather than falling back to an embedded value.
That design is especially important when the same config is used across development, staging, and production. A shared file with a runtime reference can be promoted safely if each environment resolves to its own scoped secret. A shared file with an inline token creates blast-radius problems because one accidental disclosure can affect every environment that reused the file.
For implementation detail around token handling and sender-constrained access, RFC 9700: Best Current Practice for OAuth 2.0 Security is a strong external reference. Where the runtime uses OAuth-style access, RFC 8707: Resource Indicators for OAuth 2.0 helps bind the token to the correct target resource.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP API Security Top 10 addresses the attack surface, NIST SP 800-53 Rev 5 and CIS Controls v8 set the technical controls, and ISO/IEC 27001:2022 defines the regulatory obligations.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP API Security Top 10 | API2 — Broken Authentication | Inline API tokens directly affect API authentication security. |
| Recommendation — Remove embedded tokens and enforce runtime-only credential resolution. | ||
| NIST SP 800-53 Rev 5 | IA-5 — Authenticator Management | API tokens need lifecycle control, storage, rotation, and revocation. |
| AC-6 — Least Privilege | Runtime resolution should limit where a token can be read and used. | |
| Recommendation — Store tokens outside config and rotate them through managed authenticator processes. Restrict secret access to the smallest set of processes that must resolve it. | ||
| ISO/IEC 27001:2022 | A.8.24 — Use of cryptography | Secret handling and protected storage support secure treatment of embedded credentials. |
| Recommendation — Protect stored tokens with controlled secret management and strong cryptographic safeguards. | ||
| CIS Controls v8 | CIS-5 — Account Management | Shared config tokens behave like managed credentials with rotation and revocation needs. |
| Recommendation — Track API tokens as managed credentials and remove them from shared configuration files. | ||
Practitioner Guidance
What to verify: Confirm that the MCP config contains no recoverable secret material, including old token values in comments, defaults, example blocks, or test fixtures. If a token must exist anywhere, verify that it is stored only in the vault path or runtime secret reference that the config points to.
Common mistake: Teams often replace one hard-coded token with another, such as an environment variable that is still materialised in deployment manifests, logs, or shared dotfiles. That is an improvement only if the new mechanism meaningfully reduces exposure and supports rotation without editing the config again.
What good looks like: The config can be shared publicly without granting access, secret access is limited to the smallest necessary runtime, and rotation does not require redistributing the configuration file.
Practitioner takeaway: Treat inline tokens as a design smell, not a convenience. If the file can authenticate by itself, it is no longer just configuration, it is a secret distribution mechanism.
Related resources from NHI Mgmt Group
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Reviewed and updated by the NHIMG editorial team on October 10, 2026.
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