> ## Documentation Index > Fetch the complete documentation index at: https://docs.mcpscore.dev/llms.txt > Use this file to discover all available pages before exploring further. # Rules Reference > Every rule mcpscore runs — generated from the rule registry, so it cannot drift from the code. Every rule mcpscore runs, generated from the rule registry (`make docs-rules`) — this page cannot drift from the code. * **Rule ID** is the stable machine contract used in JSON reports and CI. * **Weight** is the severity's contribution to the score when the rule passes. * **Applies to** is the spec-version range; outside it the rule is skipped and excluded from the maximum score (see the [methodology](/methodology#multi-spec-version-scoring)). ## Protocol Version | Rule ID | Name | Severity | Weight | Applies to | | --------------------------------- | ----------------------------------------- | -------- | ------ | ------------ | | `protocol_version_allowed` | MCP Protocol Version - Allowed Versions | CRITICAL | 5 | all versions | | `protocol_version_not_deprecated` | MCP Protocol Version - Deprecated Version | HIGH | 3 | all versions | | `protocol_version_latest` | MCP Protocol Version - Latest Version | MEDIUM | 2 | all versions | ## Server Info | Rule ID | Name | Severity | Weight | Applies to | | ----------------------------- | ---------------------------------- | -------- | ------ | ------------ | | `server_name_present` | Server Info - Name Present | CRITICAL | 5 | all versions | | `server_version_present` | Server Info - Version Present | HIGH | 3 | all versions | | `server_title_present` | Server Info - Title Present | MEDIUM | 2 | all versions | | `server_instructions_present` | Server Info - Instructions Present | LOW | 1 | all versions | ## Capabilities | Rule ID | Name | Severity | Weight | Applies to | | ----------------------------------- | ------------------------------------------------ | -------- | ------ | ------------ | | `capability_tools_present` | Capabilities - Tools Present | CRITICAL | 5 | all versions | | `capability_tools_list_changed` | Capabilities - Tools listChanged Implemented | HIGH | 3 | all versions | | `capability_prompts_present` | Capabilities - Prompts Present | CRITICAL | 5 | all versions | | `capability_prompts_list_changed` | Capabilities - Prompts listChanged Implemented | HIGH | 3 | all versions | | `capability_resources_present` | Capabilities - Resources Present | CRITICAL | 5 | all versions | | `capability_resources_list_changed` | Capabilities - Resources listChanged Implemented | HIGH | 3 | all versions | | `capability_resources_subscribe` | Capabilities - Resources subscribe Implemented | HIGH | 3 | all versions | | `capability_logging_present` | Capabilities - Logging Present | MEDIUM | 2 | all versions | ## Security | Rule ID | Name | Severity | Weight | Applies to | | ------------------------------------- | ----------------------------------- | -------- | ------ | ------------ | | `security_tls_enabled` | HTTPS/TLS Enabled | CRITICAL | 5 | all versions | | `security_malformed_request_handling` | Malformed Request Handling | MEDIUM | 2 | all versions | | `security_error_data_leak` | No Sensitive Data in Error Messages | MEDIUM | 2 | all versions | ## Tools | Rule ID | Name | Severity | Weight | Applies to | | ---------------------------------- | ----------------------------------------------------- | -------- | ------ | ------------ | | `tools_at_least_one` | Tools - At least one tool must exist | CRITICAL | 5 | all versions | | `tools_name_present_in_all` | Tools - All tools must have a Name | CRITICAL | 5 | all versions | | `tools_names_unique` | Tools - All tool names must be unique | CRITICAL | 5 | all versions | | `tools_names_valid_format` | Tools - All tool names must follow the format | HIGH | 3 | all versions | | `tools_title_present_in_all` | Tools - All tools must have a Title | HIGH | 3 | all versions | | `tools_description_present_in_all` | Tools - All tools must have a Description | HIGH | 3 | all versions | | `tools_input_schema_valid` | Tools - All tools must have a valid input schema | HIGH | 3 | all versions | | `tools_output_schema_valid` | Tools - All tools must have a valid output schema | HIGH | 3 | all versions | | `tools_annotations_present` | Tools - All tools should declare behavior annotations | MEDIUM | 2 | all versions | ## Transport | Rule ID | Name | Severity | Weight | Applies to | | --------------------------- | ------------------------- | -------- | ------ | ------------ | | `transport_streamable_http` | Streamable HTTP Transport | LOW | 1 | all versions | ## Resources | Rule ID | Name | Severity | Weight | Applies to | | ------------------------------- | --------------------------------------------------- | -------- | ------ | ------------ | | `resources_description_present` | Resources - All resources should have a description | MEDIUM | 2 | all versions | ## Prompts | Rule ID | Name | Severity | Weight | Applies to | | ------------------------------ | --------------------------------------------------- | -------- | ------ | ------------ | | `prompts_description_present` | Prompts - All prompts should have a description | MEDIUM | 2 | all versions | | `prompts_arguments_documented` | Prompts - All prompt arguments should be documented | LOW | 1 | all versions | ## Readiness rules (separate score) These rules assess readiness for MCP **2026-07-28** on the independent readiness axis — they never affect the main score. See the [methodology](/methodology#the-readiness-score-separate-informative) for the normative citations behind each rule. | Rule ID | Name | Severity | Weight | Applies to | | ------------------------------------------ | ------------------------------------------------- | -------- | ------ | ------------ | | `readiness_2026_server_discover` | Readiness 2026-07-28 - server/discover | CRITICAL | 5 | all versions | | `readiness_2026_stateless_request` | Readiness 2026-07-28 - stateless requests | CRITICAL | 5 | all versions | | `readiness_2026_meta_validation` | Readiness 2026-07-28 - \_meta validation | HIGH | 3 | all versions | | `readiness_2026_header_validation` | Readiness 2026-07-28 - HTTP header validation | HIGH | 3 | all versions | | `readiness_2026_cache_metadata` | Readiness 2026-07-28 - caching hints | HIGH | 3 | all versions | | `readiness_2026_unsupported_version_error` | Readiness 2026-07-28 - unsupported-version errors | MEDIUM | 2 | all versions | | `readiness_2026_error_code_migration` | Readiness 2026-07-28 - error-code migration | MEDIUM | 2 | all versions | | `readiness_2026_result_type` | Readiness 2026-07-28 - resultType on results | MEDIUM | 2 | all versions | | `readiness_2026_deprecated_features` | Readiness 2026-07-28 - deprecated features | MEDIUM | 2 | all versions | | `readiness_2026_tool_schema_dialect` | Readiness 2026-07-28 - tool schema dialect | LOW | 1 | all versions | | `readiness_2026_no_session_id` | Readiness 2026-07-28 - no session IDs | HIGH | 3 | all versions | | `readiness_2026_removed_methods` | Readiness 2026-07-28 - removed methods | MEDIUM | 2 | all versions |