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Merriam Webster

by io.github.pipeworx-io
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Define

define
Read-onlyIdempotent

Look up a word in the Merriam-Webster dictionary — the authoritative American English dictionary. Returns word definitions (short definitions), part of speech (noun, verb, adjective, etc.), pronunciation, and etymology (word origin). When the word is not found, returns close spelling suggestions instead. Example: define({ word: "ephemeral" })

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
wordYesThe word to look up, e.g. "ephemeral", "serendipity", "run"
_apiKeyNoOptional — your own Merriam-Webster keys as DICT_KEY:THES_KEY for higher limits; omit to use the shared Pipeworx key.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changed
    • changedInput schema / examples
      Previous value: -[
-  {
-    "word": "ephemeral"
-  },
-  {
-    "_apiKey": "your-merriam-webster-dict-key:your-merriam-webster-thes-key",
-    "word": "serendipity"
-  }
-]New value: +[
+  {
+    "word": "ephemeral"
+  },
+  {
+    "word": "serendipity"
+  }
+]
  2. Added

TDQS

A3.6/5.0
Behavior4/5

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false assuredly the tool is safe to invoke. The description additionally discloses the not-found behavior (spelling suggestions) and the return contents, which goes beyond the annotations. This context is valuable and consistent with 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?

Three compact sentences with no fluff. The first sentence front-loads the action and resource, the second lists outputs and fallback, and the third gives a concrete example. Every sentence earns its place, making it easy for an agent to parse quickly.

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?

For a simple two-parameter lookup tool, the description adequately covers the essential context: authoritative source, output fields, not-found behavior, and a call example. It does not detail output formatting or rate limits, but the annotations cover the safety profile and the schema covers parameters, so nothing critical is missing.

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 both 'word' and '_apiKey' are already semantically defined in the input schema. The description's example call reinforces the 'word' parameter usage but does not add new semantic information beyond what the schema provides. The baseline of 3 is appropriate.

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 states the action ('Look up a word') and the resource ('Merriam-Webster dictionary'), and enumerates specific outputs: definitions, part of speech, pronunciation, and etymology. It also covers the not-found fallback to spelling suggestions. However, it does not explicitly distinguish this tool from the sibling 'thesaurus' tool, 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 Guidelines2/5

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

There is no guidance on when to use this tool versus alternatives such as the thesaurus or other lookup tools. The description explains what the tool does but never states the conditions for choosing it or mentions any exclusions. For an agent scanning many siblings, this is a notable gap.

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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