STEM Calc MCP

Limiting reagent

limiting_reagent

Read-only

Determine the limiting reagent and theoretical yield from a chemical equation and the grams of each reactant; also reports leftover excess reactant amounts.

Instructions

Find the limiting reagent and theoretical yield for a reaction. Pass the unbalanced or balanced equation and the grams of every reactant. It balances the equation first, then reports the limiting reagent, the theoretical yield of a product in grams and moles, and the grams left over of each excess reactant.

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": {
      "equation": "<equation>",
      "reactants": "<reactants>"
    },
    "name": "limiting_reagent"
  }
}

Input Schema

Name	Required	Description
`product`	No	The product to report the yield for, written as in the equation. Defaults to the first product.
`equation`	Yes	The reaction, like N2 + H2 -> NH3.
`reactants`	Yes	The grams available of every reactant.

Output Schema

Name	Required	Description	Default
`product`	Yes
`balanced`	Yes
`limiting`	Yes
`theoreticalYieldGrams`	Yes
`theoreticalYieldMoles`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Addedv0.1.3Nov 2, 2026

TDQS

A4.2/5.0

Behavior4/5

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

Annotations already cover the safety profile (readOnlyHint, closed-world), and the description adds genuine behavioral detail: it balances first, then reports limiting reagent, yield in grams and moles, and leftover grams of each excess reactant. More than the annotations, though the output schema also carries some of the return-value information.

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?

Three sentences, all load-bearing: purpose first, required input second, computed output third. No repetition, no filler.

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?

Only 3 parameters, full schema coverage, annotations present, and an output schema exists. The description covers what the tool does, what it needs, and what it produces — nothing an agent needs to call it correctly is missing.

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 coverage is 100%, so the baseline is 3, but the description adds meaning beyond it: the equation may be unbalanced or balanced, and grams must be supplied for every reactant, not just one. The optional product parameter's default behavior is left to the schema.

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 and resource: 'Find the limiting reagent and theoretical yield for a reaction.' The note that it 'balances the equation first' implicitly separates it from the balance_equation sibling, but no sibling is ever named explicitly.

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?

'Pass the unbalanced or balanced equation and the grams of every reactant' tells the agent exactly what input is needed and clarifies that pre-balancing is not required, which is a real usage constraint. There is no explicit when-not or named alternative (e.g. plain stoichiometry for a single reactant).

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

Deploy Server