reference-data-mcp-server

Element Search

ref_element_search

Read-only

Filter periodic table elements by category, group, period, atomic number range, or atomic mass range. At least one filter is required. Returns matching elements as a summary list. Use ref_element_lookup for the full record on a specific element. Valid categories: alkali metal, alkaline earth metal, transition metal, post-transition metal, metalloid, reactive nonmetal, noble gas, lanthanide, actinide.

Input Schema

TableJSON Schema

Name	Required	Description
`group`	No	Periodic table group number (1–18). Lanthanides and actinides have no group.
`period`	No	Periodic table period (1–7).
`category`	No	Element category (partial match): alkali metal, alkaline earth metal, transition metal, post-transition metal, metalloid, reactive nonmetal, noble gas, lanthanide, actinide.
`atomic_mass_range`	No	Inclusive range of atomic mass in unified atomic mass units.
`atomic_number_range`	No	Inclusive range of atomic numbers to include.

Output Schema

TableJSON Schema

Name	Required	Description
`error`	No	Present when the call failed. Absent on success.
`notice`	No	Recovery hint when no elements matched — echoes active filters and suggests how to broaden.
`results`	No	Matching element summaries.
`totalMatches`	No	Number of elements matching all filters.
`appliedFilters`	No	Active filters applied to the search.

Schema Changelog

Changes observed during successful MCP inspections.

First observedSep 20, 2026

TDQS

A4.5/5.0

Behavior4/5

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

Annotations already mark the tool as read-only, and the description adds useful behavioral context: it returns a summary list and requires at least one filter. This exceeds what the schema alone conveys without contradicting the annotations.

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 action and filter options, then gives requirements, output shape, and sibling routing. The category list is useful but partially redundant with the schema's own list, keeping it just shy of top score.

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?

Covers what the tool returns, when it must be used, and which sibling to use for full records; the output schema handles return details. It does not specify multi-filter combination semantics, but that is not clearly necessary for this simple search tool.

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. The description adds the crucial constraint that at least one filter must be supplied even though the schema lists zero required parameters, and it enumerates valid category values.

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 opens with a specific verb ('Filter') and resource ('periodic table elements'), and enumerates the exact filter dimensions. It also distinguishes itself from ref_element_lookup by stating that lookup provides the full record for a specific element.

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

Usage Guidelines5/5

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

It explicitly states that at least one filter is required, which defines when the tool is applicable. It also routes users to ref_element_lookup for full records, giving clear guidance on which sibling to choose.

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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