--- title: "Changelog" description: "Version history of the MCP Description (mcpdesc) specification." source: "https://mcpdesc.org/docs/specification/changelog/" --- Mirrored specification This changelog mirrors the canonical [spec/CHANGELOG.md](https://github.com/cisco-open/mcptoolkit-contract/blob/main/spec/CHANGELOG.md)of `cisco-open/mcptoolkit-contract`. It spans all versions; each released version’s pages are frozen under `/docs/specification//`. Where this page differs from upstream, upstream wins. All notable changes to the MCP Description Specification are documented here. The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/). The specification uses versioning aligned with its `mcpdesc` field. ## \[0.7.0\] — 2026-03-23 ### Changed * **Simplified tags to flat structure** — removed hierarchical nesting. The Tag Object no longer includes a recursive `tags` property. All tags are now declared in a flat array at the root level. * **Tag uniqueness requirement simplified** — tag names MUST be unique across all tags (previously “across the entire tag tree”). * **Tag reference validation simplified** — per-entity tags must reference tag names declared in the root `tags` array (no nesting levels to traverse). * **Added `uniqueItems: true` constraint** to per-entity `tags` arrays on tools, resources, resource templates, and prompts to prevent duplicate tag references. ### Removed * **Removed hierarchical tag support** — Tag Objects no longer support nested `tags` arrays. The tag taxonomy is now a simple flat list. ### Updated * **Section 12 (Tags)** — completely rewritten to reflect flat tag structure. Removed hierarchical examples and references to “tag tree” and “nesting levels”. * **All examples** — converted from hierarchical tags to flat tag lists (stdio-server, http-server, full-featured examples in both JSON and YAML formats). ## \[0.6.0\] — 2026-03-20 ### Removed * **Removed the `metadata` object** from the root document structure. The `authors`, `documentation`, and `repository` fields are redundant with `info.contact` and `info.websiteUrl`, or belong in vendor extensions. * **Removed the `lifecycle` object** from the root document structure. Server lifecycle management belongs in a server manifest or registry, not in a static capability description. ### Added * **Root-level `tags` array** with structured Tag Objects (`name`, `description`, `tags`) replacing `metadata.tags`. Tags support hierarchical nesting via nested `tags` arrays (Option C). Tag names MUST be globally unique across the entire tree. * **Tag reference validation requirement** — per-entity `tags` on tools, resources, resource templates, and prompts MUST reference tag names declared in the root `tags` array when present. Undeclared tag references are a validation error. ### Changed * **Section 12** rewritten from “Metadata” to “Tags” — defines the Tag Object, uniqueness constraints, and tag reference semantics. * **Sections 9, 10, 11** — per-entity `tags` description updated with normative cross-reference to Section 12.3 tag declaration requirement. * **Section 3** root object table — `metadata` and `lifecycle` rows removed; `tags` row added. * **Sections renumbered** — removal of lifecycle (formerly Section 12) shifts Tags to 12, Specification Extensions to 13, Serialization to 14, Conformance to 15. ## \[0.5.2\] — 2026-03-18 ### Changed * **Documented MCP `Implementation` type provenance in the Info Object** — `name`, `title`, `description`, `version`, `icons`, and `websiteUrl` are now explicitly traced to the MCP `Implementation` type returned in the `initialize` response (`serverInfo`), with protocol version annotations: * `title` — MCP `BaseMetadata`, since 2025-06-18 * `description` — MCP `Implementation`, since 2025-06-18 * `websiteUrl` — MCP `Implementation`, since 2025-11-25 * `icons` — MCP `Implementation` (via `Icons` mixin), since 2025-11-25 * **Updated Info Object example** to include `icons` and `websiteUrl` fields * **Clarified `contact` and `license`** as OpenAPI-style additions not present in the MCP `Implementation` type ## \[0.5.1\] — 2026-03-17 ### Changed * **Removed `_generated` from the core MCP Description specification** (`mcpdesc: "0.5.1"`), including the root object definition and current schema. * **Updated Cisco extension to `x-cisco-metadata` v0.2.0 shape** with extension-level `version` and nested `dump` payload * **Removed `_generated` from Cisco extension examples**, with provenance retained in `x-cisco-metadata.dump` (`toolName`, `toolVersion`, `createdAt`) ## \[0.5.0\] — 2026-03-17 ### Changed * **Renamed `transport` field to `transports`** (plural) for consistency with `tools`, `resources`, `prompts` and OpenAPI’s `servers` — see [DECISION-001](https://github.com/cisco-open/mcptoolkit-contract/blob/main/docs/maintainers/design/mcp-description/DECISION-001-transports-array.md) * **Added transport-scoped `security`** — each transport MAY include its own `security` array that overrides the root-level default (see Section 6.4) * Root-level `security` is now the default; transport-level `security` overrides it (OpenAPI-style inheritance) ## \[0.4.0\] — 2026-03-16 ### Added * MCP 2025-11-25 support: icons, websiteUrl, task capabilities, tool execution properties * Tool `outputSchema` with explicit `$schema` dialect support (MCP 2025-06-18+) * Tool `execution.taskSupport` property for task-augmented execution (MCP 2025-11-25+) * `icons` definition for server, tools, resources, resource templates, and prompts * `capabilities.tasks` for task-augmented request support * `capabilities.completions` and `capabilities.logging` declarations ### Changed * **Renamed `mcpspec` field to `mcpdesc`** to clearly distinguish the description format version from the MCP protocol specification version * `protocolVersion` enum now includes `2025-11-25` * Tool `annotations` now supports `additionalProperties` for forward compatibility ## \[0.3.0\] — 2026-01-15 ### Added * `title` field on all MCP entities (BaseMetadata, since MCP 2025-06-18) * Tool `outputSchema` for structured tool output * `_meta` protocol-reserved metadata on tools, resources, resource templates, and prompts * `tags` for categorization on tools, resources, resource templates, and prompts * `deprecated` flag on tools, resources, resource templates, and prompts ### Changed * Aligned more closely with MCP 2025-06-18 protocol structures ## \[0.1.0\] — 2025-11-01 ### Added * Initial specification draft * Core document structure: `mcpspec`, `info`, `transport`, `tools`, `resources`, `resourceTemplates`, `prompts` * Transport definitions: `streamable-http`, `stdio`, `sse` * Security schemes aligned with OpenAPI 3.1 * `capabilities` object from MCP InitializeResult * `metadata` for authors, documentation, repository, tags * `_generated` provenance tracking * Specification extension mechanism (`x-` prefix) * `anyOf` constraint requiring at least one of tools, resources, resourceTemplates, or prompts