{ "openapi": "3.1.1", "info": { "title": "Emoji Cipher Playground API", "version": "1.0.0", "summary": "Turn secret notes into emoji and back: substitution, Caesar shift and base-emoji.", "description": "Every endpoint performs the same calculation as the human page and returns inputs, result, units, assumptions, sources, warnings and computedAt. MCP endpoint: /mcp." }, "servers": [ { "url": "https://emojicipherplayground.usefulweb.site" } ], "paths": { "/api/v1/calculate": { "post": { "operationId": "calculate", "summary": "Turn secret notes into emoji and back: substitution, Caesar shift and base-emoji.", "description": "Encode or decode text with three emoji ciphers: a keyed substitution (your key shuffles the emoji alphabet), a Caesar shift over an emoji alphabet, or base-emoji, which turns every UTF-8 byte into one of 256 emoji so any text survives. Round trips are exact β€” and the tool shows why none of this is real encryption.\n\nMethodology:\n- Letter schemes map a–z and 0–9 to 36 emoji (🍎 a, 🐝 b, 🐱 c … and clock faces for digits). Keyed substitution shuffles that alphabet with a generator seeded by your key; Caesar shifts letters by k (mod 26) and digits by k (mod 10) before mapping.\n- Capital letters get the marker πŸ”Ό in front. Characters that would be ambiguous (the alphabet emoji themselves, πŸ”Ό, the escape emoji πŸ”£ and the invisible emoji variation selector) are written as πŸ”£ + character. Everything else (spaces, punctuation, accents) passes through unchanged. This makes decode(encode(text)) exact, which the tool verifies on every run.\n- Base-emoji encodes the UTF-8 bytes of the text, one emoji per byte, using a fixed table of 256 emoji (U+1F300 upwards); an optional key shuffles the table. It works for any text, including emoji, but makes messages about 4Γ— longer in code points.\n- Security: none. Letter ciphers keep word lengths, spaces and letter frequencies (the most common emoji is probably β€œe”), so frequency analysis breaks them in minutes; Caesar has only 26 keys. Base-emoji is an encoding, like Base64 β€” with the standard table anyone can decode it. Use real encryption (e.g. age, GPG or an end-to-end encrypted messenger) for secrets.\n\nA toy for puzzles, games and party invitations. It does not protect anything.", "tags": [ "fun" ], "x-mcp-tool": "emoji_cipher_playground", "requestBody": { "required": true, "content": { "application/json": { "schema": { "$ref": "#/components/schemas/EmojiCipherPlaygroundInput" }, "examples": { "example1": { "summary": "Secret note with a keyed substitution", "value": { "action": "encode", "scheme": "substitution", "text": "Meet me at 7 by the old oak tree!", "key": "picnic" } }, "example2": { "summary": "Caesar shift 3", "value": { "action": "encode", "scheme": "caesar", "text": "Hello World", "shift": 3 } }, "example3": { "summary": "Base-emoji round trip (any text, even emoji)", "value": { "action": "encode", "scheme": "base-emoji", "text": "Grüße πŸ‘‹", "key": "" } }, "example4": { "summary": "Decode a Caesar message", "value": { "action": "decode", "scheme": "caesar", "text": "πŸ”ΌπŸπŸ‹πŸ±πŸ±πŸΆ πŸΆπŸ‹ πŸ•?", "shift": 3 } } } } } }, "responses": { "200": { "description": "Calculation result envelope.", "content": { "application/json": { "schema": { "$ref": "#/components/schemas/EmojiCipherPlaygroundResult" } } } }, "400": { "description": "Malformed JSON body.", "content": { "application/problem+json": { "schema": { "$ref": "#/components/schemas/Problem" } } } }, "422": { "description": "Invalid input (see errors[]).", "content": { "application/problem+json": { "schema": { "$ref": "#/components/schemas/Problem" } } } }, "429": { "description": "Rate limit exceeded (see Retry-After).", "content": { "application/problem+json": { "schema": { "$ref": "#/components/schemas/Problem" } } } } } } }, "/api/v1/tool": { "get": { "operationId": "getToolDefinition", "summary": "Inputs, output schema and examples for this tool", "responses": { "200": { "description": "Tool definition.", "content": { "application/json": { "schema": { "type": "object" } } } } } } } }, "components": { "schemas": { "Problem": { "type": "object", "description": "RFC 9457 problem details. 422 responses include per-field `errors`.", "required": [ "type", "title", "status", "detail" ], "properties": { "type": { "type": "string" }, "title": { "type": "string" }, "status": { "type": "integer" }, "detail": { "type": "string" }, "code": { "type": "string" }, "errors": { "type": "array", "items": { "type": "object", "required": [ "field", "message" ], "properties": { "field": { "type": "string" }, "message": { "type": "string" } } } } } }, "EmojiCipherPlaygroundInput": { "type": "object", "additionalProperties": false, "properties": { "action": { "title": "Action", "type": "string", "enum": [ "encode", "decode" ], "default": "encode" }, "scheme": { "title": "Cipher", "type": "string", "enum": [ "substitution", "caesar", "base-emoji" ], "default": "substitution" }, "text": { "title": "Text", "type": "string", "maxLength": 5000 }, "key": { "title": "Key", "description": "Substitution: shuffles the emoji alphabet. Base-emoji: optional shuffle of the byte table (empty = standard table). Not used by Caesar.", "type": "string", "maxLength": 100, "default": "emoji" }, "shift": { "title": "Caesar shift", "description": "Letters move by this many places (mod 26), digits too (mod 10).", "type": "integer", "minimum": -100, "maximum": 100, "default": 3 } }, "required": [ "text" ] }, "EmojiCipherPlaygroundResult": { "type": "object", "additionalProperties": false, "required": [ "schemaVersion", "tool", "computedAt", "inputs", "summary", "result", "units", "assumptions", "sources", "warnings", "presentation", "links" ], "properties": { "schemaVersion": { "type": "string", "const": "1.0" }, "tool": { "type": "object", "additionalProperties": false, "required": [ "id", "name", "version" ], "properties": { "id": { "type": "string" }, "name": { "type": "string" }, "version": { "type": "string" } } }, "computedAt": { "type": "string", "format": "date-time" }, "inputs": { "type": "object", "description": "Normalised inputs actually used, including applied defaults." }, "summary": { "type": "string" }, "result": { "type": "object", "additionalProperties": false, "required": [ "action", "scheme", "output", "inputLength", "outputLength", "roundTrip", "alphabet", "topSymbols", "keySpaceBits" ], "properties": { "action": { "type": "string", "enum": [ "encode", "decode" ] }, "scheme": { "type": "string", "enum": [ "substitution", "caesar", "base-emoji" ] }, "output": { "type": "string" }, "inputLength": { "type": "integer", "description": "Unicode code points." }, "outputLength": { "type": "integer", "description": "Unicode code points." }, "roundTrip": { "type": "boolean", "description": "Encode: decoding the output gives back the input exactly. Decode: encoding the output gives back the input (ignoring emoji variation selectors)." }, "alphabet": { "type": "array", "items": { "type": "object", "additionalProperties": false, "required": [ "plain", "emoji" ], "properties": { "plain": { "type": "string" }, "emoji": { "type": "string" } } } }, "topSymbols": { "type": "array", "items": { "type": "object", "additionalProperties": false, "required": [ "symbol", "count" ], "properties": { "symbol": { "type": "string" }, "count": { "type": "integer" } } } }, "keySpaceBits": { "type": "number", "description": "log2 of the number of possible keys β€” large or not, frequency analysis breaks these ciphers." } } }, "units": { "type": "object", "additionalProperties": { "type": "string" } }, "assumptions": { "type": "array", "items": { "type": "string" } }, "sources": { "type": "array", "items": { "type": "object", "additionalProperties": false, "required": [ "title" ], "properties": { "title": { "type": "string" }, "url": { "type": "string" }, "publisher": { "type": "string" }, "retrievedAt": { "type": "string" }, "note": { "type": "string" } } } }, "warnings": { "type": "array", "items": { "type": "string" } }, "presentation": { "type": "array", "items": { "type": "object" }, "description": "Display blocks used by the human page (same data)." }, "links": { "type": "object", "additionalProperties": false, "required": [ "human", "api", "openapi", "methodology" ], "properties": { "human": { "type": "string", "format": "uri" }, "api": { "type": "string", "format": "uri" }, "openapi": { "type": "string", "format": "uri" }, "methodology": { "type": "string", "format": "uri" } } } } } } } }