ruby-sdk/test/mcp/tool/output_schema_test.rb
Koichi ITO 99cbefc610 Allow $ref in Tool::Schema for protocol version 2025-11-25
`Tool::Schema` rejected `$ref` with an `ArgumentError`.
Earlier MCP spec versions (2024-11-05 through 2025-06-18) did not define
a JSON Schema dialect or reference the `$ref` keyword. `inputSchema` was described
only as "JSON Schema defining expected parameters" with no further constraints:

- https://modelcontextprotocol.io/specification/2024-11-05/server/tools
- https://modelcontextprotocol.io/specification/2025-06-18/server/tools

The MCP spec 2025-11-25 introduced a "JSON Schema Usage" section that adopts
JSON Schema 2020-12 as the default dialect. Since `$ref` is a core keyword in 2020-12,
it is now allowed for protocol version 2025-11-25 and later.

- https://modelcontextprotocol.io/specification/2025-11-25/basic#json-schema-usage
- https://modelcontextprotocol.io/specification/2025-11-25/server/tools
- https://json-schema.org/draft/2020-12/release-notes

For backward compatibility with older protocol versions (2025-06-18 and earlier),
`Server#validate!` continues to raise `ArgumentError` when a tool input schema contains `$ref`.
This preserves the existing behavior for servers targeting those spec versions.
2026-02-27 14:33:36 +09:00

201 lines
6.8 KiB
Ruby

# frozen_string_literal: true
require "test_helper"
module MCP
class Tool
class OutputSchemaTest < ActiveSupport::TestCase
test "to_h returns a hash representation of the output schema" do
output_schema = OutputSchema.new(properties: { result: { type: "string" } }, required: ["result"])
assert_equal(
{ type: "object", properties: { result: { type: "string" } }, required: ["result"] },
output_schema.to_h,
)
end
test "validate_result validates result against the schema" do
output_schema = OutputSchema.new(properties: { result: { type: "string" } }, required: ["result"])
assert_nothing_raised do
output_schema.validate_result({ result: "success" })
end
end
test "validate_result validates result with additional properties against the schema when additionalProperties set to nil (default)" do
output_schema = OutputSchema.new(properties: { result: { type: "string" } }, required: ["result"])
assert_nothing_raised do
output_schema.validate_result({ result: "success", extra: 123 })
end
end
test "validate_result validates result with additional properties against the schema when additionalProperties set to true" do
output_schema = OutputSchema.new(properties: { result: { type: "string" } }, required: ["result"], additionalProperties: true)
assert_nothing_raised do
output_schema.validate_result({ result: "success", extra: 123 })
end
end
test "validate_result raises error with additional properties when additionalProperties set to false)" do
output_schema = OutputSchema.new(properties: { result: { type: "string" } }, required: ["result"], additionalProperties: false)
assert_raises(OutputSchema::ValidationError) do
output_schema.validate_result({ result: "success", extra: 123 })
end
end
test "validate_result raises error for invalid result" do
output_schema = OutputSchema.new(properties: { result: { type: "string" } }, required: ["result"])
assert_raises(OutputSchema::ValidationError) do
output_schema.validate_result({ result: 123 })
end
end
test "validate_result raises error for missing required field" do
output_schema = OutputSchema.new(properties: { result: { type: "string" } }, required: ["result"])
assert_raises(OutputSchema::ValidationError) do
output_schema.validate_result({})
end
end
test "valid schema initialization" do
schema = OutputSchema.new(properties: { foo: { type: "string" } }, required: ["foo"])
assert_equal({ type: "object", properties: { foo: { type: "string" } }, required: ["foo"] }, schema.to_h)
end
test "invalid schema raises argument error" do
assert_raises(ArgumentError) do
OutputSchema.new(properties: { foo: { type: "invalid_type" } }, required: ["foo"])
end
end
test "schema without required arguments is valid" do
assert_nothing_raised do
OutputSchema.new(properties: { foo: { type: "string" } })
end
end
test "unexpected errors bubble up from validate_result" do
schema = OutputSchema.new(properties: { foo: { type: "string" } }, required: ["foo"])
JSON::Validator.stub(:fully_validate, ->(*) { raise "unexpected error" }) do
assert_raises(RuntimeError) do
schema.validate_result({ foo: "bar" })
end
end
end
test "accepts schemas with $ref references" do
schema = OutputSchema.new(
properties: {
foo: { type: "string" },
},
definitions: {
bar: { type: "string" },
},
required: ["foo"],
)
assert_includes schema.to_h.keys, :definitions
end
test "accepts schemas with $ref string key and includes $ref in to_h" do
schema = OutputSchema.new({
"properties" => {
"foo" => { "$ref" => "#/definitions/bar" },
},
"definitions" => {
"bar" => { "type" => "string" },
},
})
assert_equal "#/definitions/bar", schema.to_h[:properties][:foo][:$ref]
end
test "accepts schemas with $ref symbol key and includes $ref in to_h" do
schema = OutputSchema.new({
properties: {
foo: { :$ref => "#/definitions/bar" },
},
definitions: {
bar: { type: "string" },
},
})
assert_equal "#/definitions/bar", schema.to_h[:properties][:foo][:$ref]
end
test "== compares two output schemas with the same properties and required fields" do
schema1 = OutputSchema.new(properties: { foo: { type: "string" } }, required: ["foo"])
schema2 = OutputSchema.new(properties: { foo: { type: "string" } }, required: ["foo"])
assert_equal schema1, schema2
schema3 = OutputSchema.new(properties: { bar: { type: "string" } }, required: ["bar"])
refute_equal schema1, schema3
schema4 = OutputSchema.new(properties: { foo: { type: "string" } }, required: ["bar"])
refute_equal schema1, schema4
schema5 = OutputSchema.new(properties: { bar: { type: "string" } }, required: ["foo"])
refute_equal schema1, schema5
end
test "empty schema is valid" do
schema = OutputSchema.new
assert_equal({ type: "object" }, schema.to_h)
end
test "validates complex nested schemas" do
schema = OutputSchema.new(
properties: {
data: {
type: "object",
properties: {
items: { type: "array", items: { type: "string" } },
count: { type: "integer", minimum: 0 },
},
required: ["items"],
},
},
required: ["data"],
)
valid_result = {
data: {
items: ["item1", "item2"],
count: 2,
},
}
assert_nothing_raised do
schema.validate_result(valid_result)
end
invalid_result = {
data: {
items: [123, 456], # Should be strings
count: 2,
},
}
assert_raises(OutputSchema::ValidationError) do
schema.validate_result(invalid_result)
end
end
test "allow to declare array schemas" do
schema = OutputSchema.new({
type: "array",
items: {
properties: { foo: { type: "string" } },
required: ["foo"],
},
})
assert_equal(
{
type: "array",
items: {
properties: { foo: { type: "string" } },
required: ["foo"],
},
},
schema.to_h,
)
end
end
end
end