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Model Address Standard (MAS) v1.1

  • Version: 1.1
  • Status: Draft
  • Last Updated: July 6, 2026

1. Abstract

The Model Address Standard (MAS) defines a minimal, client-side convention for identifying an AI model using a URI fragment parameter.

MAS enables portable, shareable references to specific models without modifying HTTP semantics or requiring server-side support.

MAS does not define transport behavior, authentication, message formats, or inference parameters.

2. Scope

MAS:

  • Defines one required fragment parameter (m) and one optional fragment parameter (k)
  • Is processed entirely by clients
  • Does not alter HTTP resource identity
  • Requires no server, proxy, or infrastructure changes

If a client does not implement MAS, the URI behaves as a normal HTTP or HTTPS URL.

3. Syntax

A MAS address is any valid HTTP or HTTPS URI containing at minimum a fragment parameter m, and optionally a fragment parameter k.

3.1 General Form

https://authority[:port][/path]#m=<model-identifier>[&k=<api-key>]

MAS is layered on top of RFC 3986. This specification defines only fragment semantics and does not redefine URI grammar.

4. Required Parameter

4.1 Model Parameter (m)

The m parameter identifies the model to be used by the client.

Syntax

m = model-identifier
model-identifier = 1*( ALPHA / DIGIT / "-" / "_" / "." / "/" / ":" )

Requirements

  • m MUST be present.
  • m MUST NOT be empty.
  • m is case-sensitive.
  • Clients MUST percent-decode the value before use.
  • Clients MUST treat m as opaque and provider-defined.

MAS does not define model naming conventions.

4.2 Key Parameter (k)

The k parameter conveys an API key or token for authenticating with the model provider.

Syntax

k = api-key
api-key = 1*( ALPHA / DIGIT / "-" / "_" / "." / "~" )

Requirements

  • k MAY be present.
  • k MUST NOT be empty.
  • k is case-sensitive.
  • Clients MUST percent-decode the value before use.

When k is present, clients SHOULD include it in the Authorization header or equivalent authentication mechanism when making requests to the provider.

5. Processing Rules

When processing a MAS address:

  1. Parse the URI according to RFC 3986.
  2. Extract the fragment component.
  3. Split the fragment on & into parameters.
  4. Split each parameter on the first =.
  5. Percent-decode parameter values.
  6. Verify that m is present and non-empty.
  7. If k is present and non-empty, make its value available to the client's authentication mechanism.
  8. Ignore all remaining unknown parameters.
  9. Apply the model identifier according to client implementation.

Fragment parsing MUST occur before percent-decoding to avoid ambiguity.

6. Unknown Parameters

Clients:

  • MUST ignore unknown parameters.
  • MUST preserve unknown parameters if reserializing the URI.

Parameters known to this revision: m, k.

Future revisions of MAS may define additional standard parameters.

7. Canonical Form (Optional)

For consistent client-side comparison and deduplication:

  • The scheme and authority SHOULD be lowercase.
  • Fragment parameters SHOULD be sorted alphabetically.
  • Default or empty parameters SHOULD be omitted.
  • Percent-encoding SHOULD be minimal.

Note: Because the fragment is never sent to the server, canonicalization is purely a client concern and does not affect resource identity.

Example:

Canonical:

https://api.example.com#m=model-a&k=sk-abc123

Non-canonical:

https://API.EXAMPLE.COM#x=1&k=sk-abc123&m=model-a

8. Security Considerations

  • MAS parameters are visible in browser history, logs, and referrer headers.
  • MAS parameters are client-side metadata and MUST NOT be trusted without validation.
  • Clients SHOULD restrict acceptable model identifiers according to local policy.
  • The k parameter conveys sensitive credential data. Clients MUST handle it with the same care as any other API key or secret: avoid logging it, avoid exposing it in referrer headers, and never transmit it as part of a server-side request URI.
  • MAS does not provide authentication, authorization, or integrity guarantees beyond conveying the k parameter value.

9. Examples

https://localhost:11434#m=mistral

https://api.anthropic.com#m=claude-sonnet-4-5&k=sk-ant-abc123def456

https://bedrock.us-east-1.amazonaws.com#m=anthropic.claude-v2

https://inference.company.io:8080#m=meta-llama/Llama-2-70b

https://models.example.com#m=huggingface.co:meta-llama/Llama-2-70b

https://api.openai.com#k=sk-proj-xyz789&m=gpt-4o

10. Non-Goals

MAS does not define:

  • Sampling parameters (e.g., temperature)
  • Token limits
  • System prompts
  • API protocols
  • Streaming formats
  • Provider registries

Such concerns are intentionally out of scope.

11. References

RFC 3986 — Uniform Resource Identifier (URI): Generic Syntax