context-crystal

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crystal_extension_call

Invoke any embedded or drop-in extension by extension ID and action with a JSON payload, so new extensions work without changing MCP schemas.

Instructions

Universal dynamic dispatch invocation for any extension (embedded or drop-in executable) with structured action and JSON payload parameters, avoiding MCP schema changes for future extensions.

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": {
      "extension_id": "<extension_id>",
      "crystal_id": "<crystal_id>",
      "action": "<action>"
    },
    "name": "crystal_extension_call"
  }
}

Input Schema

Name	Required	Description
`action`	Yes	Extension action or operation name (e.g. 'send', 'list', 'review')
`payload`	No	Arbitrary structured JSON payload / parameters for the extension
`crystal_id`	Yes	Target crystal context ID
`extension_id`	Yes	Target extension identifier (e.g. 'comms', 'media', 'project_management')

Schema Changelog

Changes observed during successful MCP inspections.

Addedv1.3.0Oct 28, 2026

TDQS

B3.2/5.0

Behavior3/5

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

With no annotations, the description carries the full burden, and it does disclose a meaningful trait: dispatch can hit drop-in executables, i.e. arbitrary code with arbitrary JSON payload. It still omits side-effect profile, error behavior on unknown actions, and permission requirements, which are large gaps for a mutation-capable dispatcher.

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?

A single front-loaded sentence that leads with the verb and resource; the trailing rationale about schema stability is short and genuinely explains why the tool is generic. Slightly jargon-dense but no wasted sentences.

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

Completeness2/5

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

For a universal dispatcher with no annotations and no output schema, the description should tell the agent how to discover valid actions and payload shapes (e.g. via crystal_extension_list) and what comes back. Neither discovery path nor return shape is mentioned, leaving the agent unable to fill in the required action/payload reliably.

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

Parameters4/5

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

Schema description coverage is 100%, so the baseline is 3; the description adds that the action/payload pair is a generic structured handoff to any extension, reinforcing that payload shape is action-defined rather than fixed. It does not, however, explain that valid action values must be discovered elsewhere.

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?

States a specific verb+resource: dynamic dispatch invocation of any extension, with the distinguishing trait that it handles both embedded and drop-in executable extensions. However, it never differentiates itself from the closely named sibling crystal_extension_run (or crystal_extension_manage), so an agent cannot tell from the description alone which of the two to pick.

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

Usage Guidelines2/5

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

There is no when-to-use guidance, no prerequisites, and no named alternatives, despite three extension_* siblings in the list. The clause about avoiding MCP schema changes is a design rationale for the tool's existence, not a condition telling the agent when to invoke it.

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