Evidenceline

Look up a guideline limit

lookup_limit

Read-onlyIdempotent

Retrieve the drinking-water guideline value for a PFAS analyte under a selected rule, including unit, applicability, source citation, and WA adoption status.

Instructions

Look up the drinking-water guideline value for one analyte under one rule.

Returns the value and unit, whether the rule sets it for one analyte or for the sum of PFOS and PFHxS (applies_to), what to compare with it for the analyte asked about (compared_quantity), the source document, table and page, the rule's WA adoption status, and a one-line note in plain English. Under 'nemp-3.0', 0.07 ug/L applies to PFOS alone, PFHxS alone and their sum (Table 4, footnote a): asking for either returns that value, with the footnote quoted. Under 'current', there is no sum value. Drinking water is the only scenario loaded.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`rule`	Yes	'nemp-3.0' (PFAS NEMP 3.0, March 2025, named as adopted on the WA government page) or 'current' (ADWG values updated 2025, as listed in PFAS NEMP 3.1).
`analyte`	Yes	'PFOS', 'PFHxS', 'PFOA', 'PFBS', or 'PFOS+PFHxS' for the sum of PFOS and PFHxS.

Output Schema

TableJSON Schema

Name	Required	Description
`note`	Yes	One line in plain English.
`page`	Yes
`rule`	Yes
`unit`	Yes
`table`	Yes
`value`	Yes
`analyte`	Yes	The analyte you asked about.
`caveats`	Yes
`scenario`	Yes
`rule_name`	Yes
`wa_status`	Yes
`applies_to`	Yes	What the rule sets the value for: 'sum' means PFOS and PFHxS added together (under NEMP 3.0, Table 4, footnote a, the same value also applies to PFOS on its own and PFHxS on its own); 'single' means one analyte.
`page_basis`	Yes	'PDF page' or 'printed page'.
`source_document`	Yes
`compared_quantity`	Yes	What to compare with the value for the analyte asked about: 'sum of PFOS and PFHxS', or one analyte such as 'PFOS', or 'PFOS on its own' when a sum value also applies to PFOS alone.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Sep 24, 2026

TDQS

A4.4/5.0

Behavior4/5

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

Annotations already declare readOnlyHint=true, destructiveHint=false, and idempotentHint=true, so the description need not restate those. It adds useful context: the special behavior for 'nemp-3.0' where PFOS and PFHxS have a shared sum value, and that 'Drinking water is the only scenario loaded.' It also clarifies what the return includes (applies_to, compared_quantity, source, etc.), which goes beyond the schema.

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 compact, well-organized, and front-loads the core purpose. It uses paragraphs to separate general behavior from specific rule nuances and provides an example. No unnecessary repetition; every sentence adds information.

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 a simple two-parameter tool with a detailed output schema, the description covers the essential context: rule options, analyte values, specific edge cases (sum value, only drinking water), and return fields. It does not delve into the output schema's structure, but that is not required as the output schema is provided. Minor gaps: it doesn't mention what happens if an invalid analyte is passed, but the schema enforces allowed values.

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?

The schema already provides full descriptions for both parameters (100% coverage). The description adds value by explaining the implications of each rule and giving a concrete example of the sum behavior. It also clarifies the analyte's meaning in context (e.g., 'PFOS+PFHxS' as a sum), which enhances the schema's literal list.

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 starts with a clear verb-object pair: 'Look up the drinking-water guideline value for one analyte under one rule.' It specifies the resource (guideline limits), the scope (one analyte, one rule), and what it returns (value, unit, applies_to, compared_quantity, source, adoption status, note). It distinguishes itself from siblings like compare_rules and check_paragraph by focusing on single-rule lookup.

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 clearly explains the two rule options ('nemp-3.0' and 'current') and the analyte values accepted, providing concrete examples. It notes that 'Under 'current', there is no sum value' and that 'Drinking water is the only scenario loaded,' which prevents incorrect usage. It does not explicitly list alternatives, but the sibling names (compare_rules, search_guidelines) suggest alternatives exist; however, it gives enough context for when to use this tool.

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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