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beam_modal

Calculate exact Euler-Bernoulli natural frequencies for a uniform rectangular beam. Serves as a closed-form reference for FEM modal analysis with various boundary conditions.

Instructions

Exact Euler-Bernoulli natural frequencies of a uniform rectangular beam — the closed-form modal oracle (no solver), and the band the CalculiX fem_modal eigen-solve is gated against. f_n = (βL)_n²/(2π)·sqrt(E·I/(ρ·A·L⁴)); the beam bends in height_mm (I = width·height³/12, so a slender beam's lowest mode is the thinnest-direction bend). boundary: 'cantilever' | 'simply_supported' | 'clamped_clamped' | 'free_free' | 'clamped_pinned' (up to 5 modes each). Material via youngs_gpa+density_kg_m3, or a Materials-DB material name. Slender-beam theory — accurate while length ≫ height (thick beams need a Timoshenko correction).

Returns {boundary, n_modes, frequencies_hz, beta_l, first_mode_hz, youngs_gpa, density_kg_m3, area_mm2, I_mm4, slenderness}.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
n_modesNo
boundaryNocantilever
materialNo
width_mmYes
height_mmYes
length_mmYes
youngs_gpaNo
density_kg_m3No

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observed

TDQS

A4.4/5.0
Behavior4/5

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

With no annotations, the description carries the full burden and does well: it discloses that there is no solver, that only up to 5 modes are supported per boundary, the material alternatives, and the accuracy domain of slender-beam theory. It does not state numeric limits (min slenderness ratio) for when the result becomes unreliable, so not a 5.

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?

Front-loads the identity and formula, then physical caveats, then return shape. Dense but nearly every clause earns its place; the formula and symbol-heavy phrasing make it slightly heavier than strictly necessary for an agent.

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?

For a physics oracle with no output schema, the description compensates fully by listing the return object's fields and explaining the underlying model, units, and applicability limits. An agent has everything needed to call and interpret it.

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 0%, so the description must compensate, and it does: it enumerates all five valid `boundary` values (which the schema does not), explains `n_modes` (up to 5 each), the `youngs_gpa`+`density_kg_m3` vs `material` alternatives, and the bending direction tied to `height_mm` (I = width·height³/12). It adds little on the sheer `length_mm`/`width_mm`/`height_mm` units, but the physics context is strong.

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?

States a specific verb+resource+method: 'Exact Euler-Bernoulli natural frequencies of a uniform rectangular beam' and explicitly identifies itself as the closed-form modal oracle that fem_modal is gated against, cleanly separating it from that sibling.

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?

Establishes when this tool is appropriate (closed-form, no solver, slender beams) and when it is not ('thick beams need a Timoshenko correction'), and names the gating relationship to fem_modal. It does not spell out an explicit either/or selection rule with fem_modal, so it stops short of a 5.

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

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