Kiro MCP Server

Fork a Kiro session

kiro_session_fork

Fork a Kiro CLI session at an optional user message ID, creating a new session while leaving the original unchanged for rewind-style branching.

Instructions

Fork a session with session/fork, optionally at a user message id from kiro_session_history's rewind_points (that is /rewind). The fork is attached as a new session; the original is unchanged.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "session_id": "<session_id>"
    },
    "name": "kiro_session_fork"
  }
}

Input Schema

Name	Required	Description	Default
`message_id`	No
`session_id`	Yes	Kiro session id (sess_<uuid>).

Output Schema

Name	Required	Description	Default
`modes`	Yes
`cursor`	Yes
`commands`	Yes
`message_id`	Yes
`session_id`	Yes
`current_mode`	Yes
`context_usage`	Yes
`config_options`	Yes
`parent_session_id`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.1Nov 5, 2026

TDQS

A3.7/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare it a non-destructive, non-idempotent mutation, and the description adds the key behavioral fact that the fork becomes a new session while the original is unchanged. It does not cover permissions, rate limits, or what state carries over to the fork.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Two short sentences with the core operation front-loaded and no filler. The parenthetical '(that is /rewind)' is slightly cryptic but serves as useful shorthand.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a two-parameter tool with an output schema and clear annotations, the description covers the essential semantics: forking, optional rewind point, and original preservation. Only the omit-message_id behavior and session id retrieval are left implicit.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 50% (message_id is undocumented in the schema), and the description does compensate by tying message_id to kiro_session_history's rewind_points. However it does not explain acceptable values, whether it must be a user message, or what omitting it does beyond 'optionally'.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description names a specific verb and resource (fork a session) and clarifies the underlying operation, distinguishing it from adjacent tools like kiro_session_compact or kiro_session_new. It stops short of explicitly naming a sibling to avoid, but the intent is unambiguous.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage context is implied by the optional message_id: pass one to branch from a rewind point. There is no explicit when-to-use vs when-not guidance, e.g. fork vs new session, or what happens if a message id is omitted.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.