reference-data-mcp-server

Element Lookup

ref_element_lookup

Read-only

Look up a periodic table element by name, chemical symbol, or atomic number. Returns the full data record: atomic number, symbol, name, atomic mass (in unified atomic mass units), electron configuration, group, period, block, category (e.g., "noble gas", "transition metal"), Pauling electronegativity, density (g/cm³), melting and boiling points in kelvin, and discovery year. Properties unavailable for synthetic or insufficiently studied elements are returned as null.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`by`	No	Lookup mode: auto tries atomic number, then symbol, then name.	auto
`query`	Yes	Element name (e.g., "tungsten"), chemical symbol (e.g., "W"), or atomic number as a string (e.g., "74").

Output Schema

TableJSON Schema

Name	Required	Description
`name`	No	IUPAC element name.
`block`	No	Electron block: s, p, d, or f.
`error`	No	Present when the call failed. Absent on success.
`group`	No	Periodic table group number (1–18). Null for lanthanides and actinides.
`number`	No	Atomic number (proton count).
`period`	No	Periodic table period number (1–7).
`symbol`	No	Chemical symbol (e.g., "Fe").
`natural`	No	True if the element occurs naturally on Earth.
`category`	No	Element category (e.g., "transition metal", "noble gas", "lanthanide").
`appearance`	No	Physical appearance description. Null for synthetic elements not macroscopically observed.
`atomic_mass`	No	Standard atomic mass in unified atomic mass units (u). Null for unstable elements with no standard mass.
`radioactive`	No	True if all isotopes are radioactive (no stable isotopes).
`phase_at_stp`	No	Phase at standard temperature and pressure: Solid, Liquid, or Gas.
`discovery_year`	No	Year of discovery. Null for elements known since antiquity.
`boiling_point_k`	No	Boiling point in kelvin at standard pressure. Null for unstable or synthetic elements.
`dataset_version`	No	Data source version identifier.
`melting_point_k`	No	Melting point in kelvin at standard pressure. Null for unstable or synthetic elements.
`density_g_per_cm3`	No	Density in grams per cubic centimeter at STP. Null for synthetic or poorly studied elements.
`discovery_scientists`	No	Scientist(s) credited with discovery. Null for elements known since antiquity.
`atomic_mass_estimated`	No	True when the atomic mass is estimated or based on the most stable isotope rather than a natural abundance average.
`electron_configuration`	No	Electron configuration using noble gas shorthand (e.g., "[Ar] 3d6 4s2").
`electronegativity_pauling`	No	Pauling electronegativity scale value. Null for noble gases and heavy synthetic elements.

Schema Changelog

Changes observed during successful MCP inspections.

First observedSep 20, 2026

TDQS

A3.7/5.0

Behavior4/5

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

Annotations already declare `readOnlyHint: true`, so the description does not need to restate non-mutation. It adds useful behavioral detail beyond annotations: unavailable properties for synthetic/insufficiently studied elements are explicitly returned as null. No contradiction with annotations exists.

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?

The description is front-loaded with the core lookup behavior and then lists the returned record efficiently. The enumeration of fields is long but earns its place by specifying units and null behavior; minor restructuring could improve readability.

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

Completeness4/5

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

With an output schema present and read-only annotations, the description is nearly complete: it states accepted inputs, enumerates returned fields, and clarifies null semantics. It does not explicitly describe failure/not-found behavior or when to use a sibling search tool, which keeps it from being fully complete.

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

Parameters3/5

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

Schema description coverage is 100%, so the input schema already explains `query` and `by` well. The tool description reinforces the query forms but does not add new parameter-level semantics beyond what the schema provides.

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?

The description clearly identifies the verb ('Look up'), the resource ('periodic table element'), and the three accepted input forms. It is clear enough to distinguish from the 'search' siblings, but it does not explicitly name or contrast with `ref_element_search`, so it stops short of a 5.

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

Usage Guidelines3/5

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

The tool's use case is implied by describing exact lookups by name, symbol, or atomic number, and by enumerating the returned fields. However, there is no explicit guidance about when to choose this lookup tool over `ref_element_search` or the other reference lookup siblings, nor any stated exclusions.

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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