Runtime Options

Runtime Options

Options passed to the generated RegisterXxxClient function to customize tool registration at runtime. No regeneration needed.

import "github.com/dipjyotimetia/openapi-go-mcp/pkg/runtime"

petmcp.RegisterSwaggerPetstoreClient(s, client,
    runtime.WithNamePrefix("staging"),
    runtime.WithExtraProperties(...),
)

WithNamePrefix(prefix string)

Prepend a static prefix to every tool name registered by this call. Useful when:

• The same API is registered twice in one server (e.g. staging + prod).
• You're aggregating multiple APIs and want a namespace per upstream.

petmcp.RegisterSwaggerPetstoreClient(s, stagingClient, runtime.WithNamePrefix("staging"))
petmcp.RegisterSwaggerPetstoreClient(s, prodClient,    runtime.WithNamePrefix("prod"))

Tool getPet becomes staging_getPet and prod_getPet.

WithExtraProperties(props ...ExtraProperty)

Inject per-call context properties into every tool's input schema. The LLM is asked to provide them on every call; your code reads them from the decoded args.

Typical uses: tenant ID, request correlation token, environment selector.

petmcp.RegisterSwaggerPetstoreClient(s, client,
    runtime.WithExtraProperties(
        runtime.ExtraProperty{
            Name:        "tenant",
            Description: "Tenant ID",
            Required:    true,
        },
    ),
)

The property appears at the top of the input schema (sibling to path/query/header/body) and is available to tool handlers via the decoded arguments. If Required: true is set, calls without it are rejected before the upstream HTTP request fires.

CLI equivalents

Some options are also expressible at generation time:

Runtime option	CLI flag	Difference
WithNamePrefix	-name-prefix	CLI bakes the prefix into the generated code (less flexible). Runtime lets you choose per-registration.

There is no CLI equivalent for WithExtraProperties — extra properties are inherently a runtime concern.

Adding your own options

Options follow the standard Go functional-options pattern. Adding one means:

1. Define WithFoo(...) Option in pkg/runtime/.
2. Update ApplyConfig to handle the new field.
3. Use it from your main — the generated code calls ApplyConfig and the option flows through.

The generated Register* function does not change.

Related

• Companion Mode
• Deployment Patterns