Reference

ctx_fill

Input contract and parameters for ctx_fill.

Status by featureReviewed September 2026

MCP tool · Planning tools

Call this tool through your MCP client. Its availability depends on your active configuration and profile.

This registry contract is separate from the SDK. For terminal commands, use the CLI reference.

Parameters

Generated from the registered input schema. “Required” reflects the schema; individual actions can impose additional requirements.

budgetintegerRequired

Max token budget

pathsarrayRequired

File paths

taskstring

Intent-driven pruning target

Exact JSON schema

Inspect the complete input schema

{
  "properties": {
    "budget": {
      "description": "Max token budget",
      "type": "integer"
    },
    "paths": {
      "description": "File paths",
      "items": {
        "type": "string"
      },
      "type": "array"
    },
    "task": {
      "description": "Intent-driven pruning target",
      "type": "string"
    }
  },
  "required": [
    "paths",
    "budget"
  ],
  "type": "object"
}

Runtime description

The following is the tool's own agent-facing description, reproduced from the reviewed registry. It can contain implementation terminology; it does not expand the public stability commitment.

Read the agent-facing description

Budget-aware context fill — compress N files to fit a token budget.
WORKFLOW: pass paths[] + budget=N; task="..." enables intent-driven pruning.
ANTIPATTERN: does NOT decide which files to include — use ctx_plan for project-wide selection.
Saves tokens vs per-file reads (for many files with a budget).

Sources & versions3 references Reviewed 18 Sept 2026

mcp_manifest.rsrust/src/core/mcp_manifest.rsReviewed checkout
registry.rsrust/src/server/registry.rsReviewed checkout
dynamic_tools.rsrust/src/server/dynamic_tools.rsReviewed checkout

Core checkout: 50fbff09c9
Installed runtime: 3.10.2
SDK release: 1.1.0

Separate baselines for source, CLI/configuration and SDK contracts. Review does not certify every platform or integration.

Versions & compatibility