Problem

AddResource (Go SDK) builds its request body with "args": map[string]any{} unconditionally, then only overrides it when opts.Args != nil. So when a caller passes no args — the common case, e.g. client.AddResource(ctx, path, nil) — an empty args object is always sent.

Instances that predate #2549 (which added the args field to the resources route under model_config = ConfigDict(extra="forbid")) have no args field, so extra="forbid" rejects the request with:

body.args: Extra inputs are not permitted

i.e. AddResource fails entirely against older / hosted OpenViking endpoints.

Fix

Drop the unconditional args: {} from the payload literal and only attach args when arguments were actually provided (len(opts.Args) > 0). This is the Go counterpart of the same cross-client backward-compat sweep already merged for the other surfaces:

• Rust CLI — fix(cli): omit null/empty request fields so older instances accept them #2799 (compact_request_body)
• Python SDK — fix(sdk): omit null/empty request fields so older instances accept them #2834 (_compact_request_body)

Scope is intentionally args-only, matching #2834. All other fields, including directly_upload_media, are unchanged. The Go Find/Search paths already omit unset optionals via setString/setAny, so AddResource's empty args was the only remaining Go surface with this issue.

Note (intentional): len(opts.Args) > 0 treats nil and an explicitly-empty map[string]any{} the same — both omit the key. On this create route the server defaults args to {} (Field(default_factory=dict) from #2549), so "absent" and "present-but-empty" are equivalent; and omitting an explicit empty map is what keeps the request compatible with pre-#2549 instances. This mirrors _compact_request_body in #2834 (which is not used for PATCH/update bodies where null could mean "clear").

Tests

go test ./sdk/go passes. Added/extended coverage for all three arg states:

• TestAddResourceUploadsLocalFile — asserts args is absent when the caller passes nil
• TestAddResourceOmitsExplicitlyEmptyArgs — asserts args is absent for an explicitly-empty map
• TestAddResourceSendsArgsWhenProvided — asserts args is forwarded when populated