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Macrostrat

by io.github.pipeworx-io
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Find Units

find_units
Read-onlyIdempotent

Find geologic rock units from Macrostrat by location + age, by stratigraphic name, or by lithology. Provide lat+lng (optionally with age in millions of years, Ma), or a strat_name (e.g. "Hell Creek"), or a lith (e.g. "granite"). Returns units with formation/group, stratigraphic column, bottom/top ages (Ma) and time intervals, lithology, and max thickness. Keyless. North America and beyond.

Example tool call

This call uses example arguments supplied in the tool’s input schema.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "lat": 40.8071,
      "lng": -104.9901
    },
    "name": "find_units"
  }
}

Input Schema

NameRequiredDescriptionDefault
ageNoGeologic age in millions of years (Ma). Optional; used with lat+lng.
latNoLatitude (decimal degrees). Must be paired with lng.
lngNoLongitude (decimal degrees). Must be paired with lat.
lithNoLithology to match, e.g. "granite", "sandstone".
limitNoMax units to return (default 20).
strat_nameNoStratigraphic name to match, e.g. "Hell Creek".

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changed
    • addedInput schema / examples
      Added value: +[
+  {
+    "lat": 40.8071,
+    "lng": -104.9901
+  },
+  {
+    "age": 66,
+    "lat": 40.8071,
+    "lng": -104.9901
+  },
+  {
+    "strat_name": "Hell Creek"
+  },
+  {
+    "limit": 10,
+    "lith": "granite"
+  }
+]
  2. First observed

TDQS

A4.2/5.0
Behavior4/5

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

Annotations already state readOnlyHint=true, destructiveHint=false, etc., and the description adds useful behavioral context beyond that: 'Keyless' (no authentication needed), 'North America and beyond' (geographic scope), and the return fields ('formation/group, stratigraphic column, bottom/top ages (Ma)...'). This adds meaningful operational knowledge 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.

Conciseness5/5

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

The description is four sentences, each earning its place: purpose, input options, return values, and key facts (keyless, scope). It is front-loaded with the most important information and contains no filler or redundancy.

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?

Given the absence of an output schema, the description adequately covers what the tool returns and general context (geographic scope, keyless access). It does not mention pagination or exact-match behavior, but with 6 optional params and examples in the schema, it is sufficiently complete for an agent to invoke it correctly.

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 baseline is 3. The description mentions the three search modes (lat+lng, strat_name, lith) and the optional age, but this adds little beyond what the schema already describes for each parameter (e.g., lit says 'Lithology to match'). The description does not provide additional semantic details about parameter behavior or combinations.

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 'Find geologic rock units from Macrostrat by location + age, by stratigraphic name, or by lithology,' which clearly specifies the verb (find), resource (geologic rock units from Macrostrat), and the three distinct search modes. This distinguishes it from sibling tools like define_lithology (which likely defines a lithology term) and find_columns (which finds columns), making the purpose unmistakable.

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 explicit guidance on when to use the tool: 'Provide lat+lng (optionally with age...), or a strat_name (e.g. "Hell Creek"), or a lith (e.g. "granite")'. This gives clear context for input selection, but it does not explicitly mention exclusions or alternative tools, so it falls 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.

All Macrostrat toolsInspect
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