embedcalc-mcp

Crystal Load Capacitor Calculator

embedcalc_crystal_load_caps

Read-onlyIdempotent

Calculate the two external load capacitors for a crystal from its load capacitance and stray capacitance to prevent frequency errors.

Instructions

Compute the two external load capacitors for a crystal from its specified load capacitance: CL = C/2 + Cstray -> C = 2·(CL − Cstray).

Args: load_capacitance_pf (from crystal datasheet, e.g. 18), stray_pf (PCB+pin stray, typ. 3-5). Returns (structured): { cap_each_pf }. Example: CL=18pF, stray=5pF -> 26 pF each side. Wrong load caps = frequency pulling; don't guess.

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": {
      "load_capacitance_pf": "<load_capacitance_pf>"
    },
    "name": "embedcalc_crystal_load_caps"
  }
}

Input Schema

Name	Required	Description	Default
`stray_pf`	No	Stray capacitance (PCB traces + MCU pins) in pF, typ. 3-5
`load_capacitance_pf`	Yes	Crystal's specified CL in pF

Output Schema

Name	Required	Description	Default
`cap_each_pf`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.3.1Jul 11, 2026

TDQS

A4.5/5.0

Behavior4/5

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

Annotations already indicate read-only, idempotent, non-destructive behavior. The description adds value by explaining the formula, output structure, and consequences of incorrect input (frequency pulling). No contradiction with annotations.

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

Conciseness5/5

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

The description is concise: two sentences plus an example and warning. It is front-loaded with the formula and purpose, with no redundant information.

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

Completeness5/5

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

Given the tool's simplicity, the description covers input, formula, output structure, example, and a warning. An output schema exists (not shown) but the description already indicates the return value format. Complete for the context.

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?

Input schema coverage is 100% with descriptions for both parameters. The description adds context with example values (e.g., 18 pF, stray typ. 3-5) and explains the formula, enhancing understanding beyond the schema.

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

Purpose5/5

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

The description clearly states it computes external load capacitors for a crystal using a specific formula. The verb 'compute' and resource 'external load capacitors' are specific. It distinguishes itself from sibling calculators (e.g., other embedcalc tools) by focusing on crystal load capacitance.

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

Usage Guidelines4/5

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

The description provides an example and warns about frequency pulling from wrong values, implying use when designing crystal oscillator circuits. However, it does not explicitly state when not to use or name alternative tools, though no siblings overlap functionally.

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