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index observed

sync-day

Free no-signup group scheduling; share a link and rank times by who's free.

Should I use this

Quality & Safety

A
Description quality
100%
Schema completeness
98%
Naming quality
95%
Poisoning risk
100%
Permission match
100%
Protocol compliance
100%

Based on automated analysis of tool definitions and protocol compliance.

Context Cost

~3,370Tokens (tool definitions)
~2.8 KBTypical response size
Significant attention impact (2.63% of 128k context)

This is the approximate number of tokens consumed each time the server's tools are loaded into a model's context. Higher counts reduce the attention available for other tasks.

Install

One-Click Install

Add this to your `claude_desktop_config.json` file:

{
  "mcpServers": {
    "sync-day": {
      "url": "https://sync.day/mcp/mcp"
    }
  }
}

Remote endpoints

https://sync.day/mcp/mcpstreamable-http

What it can do

Tool inventory

Tools (8)

🟢 Read-only🟡 Write🔴 Delete⚪ Unknown
🔴create_event(title, question, startDate, endDate, days, ...)

Create a sync.day availability poll and get its share link. Candidate days run from startDate to endDate (inclusive; or give days instead). Each day offers candidate START times from hourFrom, every startStepMinutes, as long as start + durationMinutes <= hourTo. Returns slug, public url (share this), adminUrl and adminKey (keep private; needed for update_event / remove_participant). Example: 周六周日下午聚餐 3 小时 -> {title:'周末聚餐', startDate:'2026-09-05', endDate:'2026-09-06', hourFrom:13, hourTo:18, durationMinutes:180, startStepMinutes:60}.

Input Schema

{
  "type": "object",
  "properties": {
    "title": {
      "type": "string",
      "minLength": 1,
      "maxLength": 60,
      "description": "Event name, max 60 chars. e.g. 周末聚餐, Team sync"
    },
    "question": {
      "description": "Optional prompt shown to participants, max 200 chars. e.g. 哪天晚上有空？",
      "type": "string",
      "maxLength": 200
    },
    "startDate": {
      "type": "string",
      "pattern": "^\\d{4}-\\d{2}-\\d{2}$",
      "description": "First candidate day, YYYY-MM-DD. e.g. 2026-09-05"
    },
    "endDate": {
      "description": "Last candidate day, inclusive, YYYY-MM-DD (same as startDate for a single day; at most 21 days). Give this or days; endDate wins when both are set.",
      "type": "string",
      "pattern": "^\\d{4}-\\d{2}-\\d{2}$"
    },
    "days": {
      "description": "Number of consecutive days from startDate (1-21); alternative to endDate.",
      "type": "integer",
      "minimum": 1,
      "maximum": 21
    },
    "hourFrom": {
      "type": "integer",
      "minimum": 0,
      "maximum": 23,
      "description": "Earliest hour of each day (0-23). e.g. 9"
    },
    "hourTo": {
      "type": "integer",
      "minimum": 1,
      "maximum": 24,
      "description": "End of each day's window, exclusive (1-24), must be > hourFrom. e.g. 22"
    },
    "durationMinutes": {
      "anyOf": [
        {
          "type": "number",
          "const": 30
        },
        {
          "type": "number",
          "const": 60
        },
        {
          "type": "number",
          "const": 90
        },
        {
          "type": "number",
          "const": 120
        },
        {
          "type": "number",
          "const": 180
        },
        {
          "type": "number",
          "const": 240
        },
        {
          "type": "number",
          "const": 480
        }
      ],
      "description": "Event length in minutes. One of 30, 60, 90, 120, 180, 240, 480."
    },
    "startStepMinutes": {
      "default": 60,
      "anyOf": [
        {
          "type": "number",
          "const": 30
        },
        {
          "type": "number",
          "const": 60
        }
      ],
      "description": "Gap between candidate start times in minutes: 30 or 60 (default 60)."
    }
  },
  "required": [
    "title",
    "startDate",
    "hourFrom",
    "hourTo",
    "durationMinutes"
  ],
  "$schema": "https://json-schema.org/draft/2020-12/schema"
}
🟢parse_event_text(text, today)

Turn a natural-language sentence (Chinese works best) into create_event input using sync.day's AI parser. Does NOT create anything; review the result, then call create_event. Example: '下周六或周日下午聚餐，大概 3 小时'.

Input Schema

{
  "type": "object",
  "properties": {
    "text": {
      "type": "string",
      "minLength": 1,
      "maxLength": 300,
      "description": "One sentence describing the event, max 300 chars."
    },
    "today": {
      "description": "Reference date for relative words like 明天/下周, YYYY-MM-DD. Defaults to today in Asia/Shanghai.",
      "type": "string",
      "pattern": "^\\d{4}-\\d{2}-\\d{2}$"
    }
  },
  "required": [
    "text"
  ],
  "$schema": "https://json-schema.org/draft/2020-12/schema"
}
🟢get_event(slug)

Read an event: settings, every candidate start key per day (startOptions), who has answered (participants with their start keys; names may repeat), the top 10 start times by head-count (ranked), the starts EVERYONE with picks can make with their votes (voteOptions), each person's vote (votes) and decidedStart. No key needed.

Input Schema

{
  "type": "object",
  "properties": {
    "slug": {
      "type": "string",
      "pattern": "^(?:[a-z]{3,7}-[a-z]{3,7}(?:-\\d{2}|-\\d{4})?|[A-Za-z0-9_-]{10})$",
      "description": "Event slug from the URL, e.g. calm-otter-4821 (sync.day/calm-otter-4821)"
    }
  },
  "required": [
    "slug"
  ],
  "$schema": "https://json-schema.org/draft/2020-12/schema"
}
🟡submit_availability(slug, identity, name, starts)

Save (or replace) one person's availability: the candidate start keys they can make, from get_event.startOptions. The person is identified by `identity`, not by name: the same identity later overwrites the same row (and can rename it), a different identity with the same name is a second participant. Keys outside the event's start options are rejected. Returns the updated ranking.

Input Schema

{
  "type": "object",
  "properties": {
    "slug": {
      "type": "string",
      "pattern": "^(?:[a-z]{3,7}-[a-z]{3,7}(?:-\\d{2}|-\\d{4})?|[A-Za-z0-9_-]{10})$",
      "description": "Event slug from the URL, e.g. calm-otter-4821 (sync.day/calm-otter-4821)"
    },
    "identity": {
      "type": "string",
      "minLength": 16,
      "maxLength": 256,
      "description": "Random secret for this person that you generate and keep per person, 16-256 chars (e.g. 32 hex chars; NOT a plain user id or name, since anyone who guesses it can act as them). Same identity = same participant; the server stores only a hash. Example: 3f9a1c77b2e04d5e8a61f0c9d2b7e415"
    },
    "name": {
      "type": "string",
      "minLength": 1,
      "maxLength": 20,
      "description": "Display name, 1-20 chars, may repeat. e.g. 小明"
    },
    "starts": {
      "maxItems": 1008,
      "type": "array",
      "items": {
        "type": "string",
        "pattern": "^\\d{4}-\\d{2}-\\d{2}T\\d{2}:\\d{2}$"
      },
      "description": "Start keys like 2026-09-05T14:00. Empty array clears this person's picks."
    }
  },
  "required": [
    "slug",
    "identity",
    "name",
    "starts"
  ],
  "$schema": "https://json-schema.org/draft/2020-12/schema"
}
🔴remove_participant(slug, name, adminKey)

Organiser only: remove one participant by name (the oldest row with that name when it repeats), together with their vote. Requires the adminKey from create_event.

Input Schema

{
  "type": "object",
  "properties": {
    "slug": {
      "type": "string",
      "pattern": "^(?:[a-z]{3,7}-[a-z]{3,7}(?:-\\d{2}|-\\d{4})?|[A-Za-z0-9_-]{10})$",
      "description": "Event slug from the URL, e.g. calm-otter-4821 (sync.day/calm-otter-4821)"
    },
    "name": {
      "type": "string",
      "minLength": 1,
      "maxLength": 20,
      "description": "Exact participant name to remove."
    },
    "adminKey": {
      "type": "string",
      "pattern": "^[A-Za-z0-9_-]{12}(?:[A-Za-z0-9_-]{12})?$",
      "description": "Organiser key returned by create_event (the ?key= part of adminUrl)."
    }
  },
  "required": [
    "slug",
    "name",
    "adminKey"
  ],
  "$schema": "https://json-schema.org/draft/2020-12/schema"
}
🟡update_event(slug, adminKey, title, question, startDate, ...)

Organiser only: change any event settings (same fields and rules as create_event; omitted fields keep their current value; endDate wins over days). Existing picks are kept; those no longer valid starts are just hidden.

Input Schema

{
  "type": "object",
  "properties": {
    "slug": {
      "type": "string",
      "pattern": "^(?:[a-z]{3,7}-[a-z]{3,7}(?:-\\d{2}|-\\d{4})?|[A-Za-z0-9_-]{10})$",
      "description": "Event slug from the URL, e.g. calm-otter-4821 (sync.day/calm-otter-4821)"
    },
    "adminKey": {
      "type": "string",
      "pattern": "^[A-Za-z0-9_-]{12}(?:[A-Za-z0-9_-]{12})?$",
      "description": "Organiser key returned by create_event (the ?key= part of adminUrl)."
    },
    "title": {
      "type": "string",
      "minLength": 1,
      "maxLength": 60,
      "description": "Event name, max 60 chars. e.g. 周末聚餐, Team sync"
    },
    "question": {
      "description": "Optional prompt shown to participants, max 200 chars. e.g. 哪天晚上有空？",
      "type": "string",
      "maxLength": 200
    },
    "startDate": {
      "type": "string",
      "pattern": "^\\d{4}-\\d{2}-\\d{2}$",
      "description": "First candidate day, YYYY-MM-DD. e.g. 2026-09-05"
    },
    "endDate": {
      "description": "Last candidate day, inclusive, YYYY-MM-DD (same as startDate for a single day; at most 21 days). Give this or days; endDate wins when both are set.",
      "type": "string",
      "pattern": "^\\d{4}-\\d{2}-\\d{2}$"
    },
    "days": {
      "description": "Number of consecutive days from startDate (1-21); alternative to endDate.",
      "type": "integer",
      "minimum": 1,
      "maximum": 21
    },
    "hourFrom": {
      "type": "integer",
      "minimum": 0,
      "maximum": 23,
      "description": "Earliest hour of each day (0-23). e.g. 9"
    },
    "hourTo": {
      "type": "integer",
      "minimum": 1,
      "maximum": 24,
      "description": "End of each day's window, exclusive (1-24), must be > hourFrom. e.g. 22"
    },
    "durationMinutes": {
      "anyOf": [
        {
          "type": "number",
          "const": 30
        },
        {
          "type": "number",
          "const": 60
        },
        {
          "type": "number",
          "const": 90
        },
        {
          "type": "number",
          "const": 120
        },
        {
          "type": "number",
          "const": 180
        },
        {
          "type": "number",
          "const": 240
        },
        {
          "type": "number",
          "const": 480
        }
      ],
      "description": "Event length in minutes. One of 30, 60, 90, 120, 180, 240, 480."
    },
    "startStepMinutes": {
      "default": 60,
      "anyOf": [
        {
          "type": "number",
          "const": 30
        },
        {
          "type": "number",
          "const": 60
        }
      ],
      "description": "Gap between candidate start times in minutes: 30 or 60 (default 60)."
    }
  },
  "required": [
    "slug",
    "adminKey"
  ],
  "$schema": "https://json-schema.org/draft/2020-12/schema"
}
🟡vote_time(slug, identity, starts, start)

Approval voting: set every start one person accepts (replaces their earlier approvals; an empty list clears them). The voter is the `identity` used in submit_availability and must have at least one start saved. Only keys listed in get_event.voteOptions are accepted; the error lists the current options otherwise. Rejected once the organiser decided. Example: {slug:'calm-otter-4821', identity:'3f9a1c77b2e04d5e8a61f0c9d2b7e415', starts:['2026-09-05T15:00','2026-09-06T10:00']}. `start` is shorthand for a single-item `starts`.

Input Schema

{
  "type": "object",
  "properties": {
    "slug": {
      "type": "string",
      "pattern": "^(?:[a-z]{3,7}-[a-z]{3,7}(?:-\\d{2}|-\\d{4})?|[A-Za-z0-9_-]{10})$",
      "description": "Event slug from the URL, e.g. calm-otter-4821 (sync.day/calm-otter-4821)"
    },
    "identity": {
      "type": "string",
      "minLength": 16,
      "maxLength": 256,
      "description": "Random secret for this person that you generate and keep per person, 16-256 chars (e.g. 32 hex chars; NOT a plain user id or name, since anyone who guesses it can act as them). Same identity = same participant; the server stores only a hash. Example: 3f9a1c77b2e04d5e8a61f0c9d2b7e415"
    },
    "starts": {
      "description": "All start keys this person accepts (from get_event.voteOptions); [] clears their approvals",
      "maxItems": 500,
      "type": "array",
      "items": {
        "type": "string",
        "pattern": "^\\d{4}-\\d{2}-\\d{2}T\\d{2}:\\d{2}$",
        "description": "Start key, e.g. 2026-09-05T15:00"
      }
    },
    "start": {
      "description": "Shorthand for starts: [start]",
      "type": "string",
      "pattern": "^\\d{4}-\\d{2}-\\d{2}T\\d{2}:\\d{2}$"
    }
  },
  "required": [
    "slug",
    "identity"
  ],
  "$schema": "https://json-schema.org/draft/2020-12/schema"
}
🟡decide_time(slug, adminKey, start)

Organiser only: settle on a start time (locks availability picking and voting; the page shows 已定). Pass start=null to reopen. Requires the adminKey from create_event.

Input Schema

{
  "type": "object",
  "properties": {
    "slug": {
      "type": "string",
      "pattern": "^(?:[a-z]{3,7}-[a-z]{3,7}(?:-\\d{2}|-\\d{4})?|[A-Za-z0-9_-]{10})$",
      "description": "Event slug from the URL, e.g. calm-otter-4821 (sync.day/calm-otter-4821)"
    },
    "adminKey": {
      "type": "string",
      "pattern": "^[A-Za-z0-9_-]{12}(?:[A-Za-z0-9_-]{12})?$",
      "description": "Organiser key returned by create_event (the ?key= part of adminUrl)."
    },
    "start": {
      "anyOf": [
        {
          "type": "string",
          "pattern": "^\\d{4}-\\d{2}-\\d{2}T\\d{2}:\\d{2}$"
        },
        {
          "type": "null"
        }
      ],
      "description": "A candidate start key of the event (normally one of voteOptions), or null to reopen."
    }
  },
  "required": [
    "slug",
    "adminKey",
    "start"
  ],
  "$schema": "https://json-schema.org/draft/2020-12/schema"
}

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Evidence

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verifiedversion not recorded8 tools
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