Locus

Web Extract

web_extract

Read the exact public URLs supplied by the caller. Locus uses a full-content extractor first and retries only failed resources through a second exact-URL scraper; it never searches for substitutes. Live billed request; the result reports credits charged.

Input Schema

TableJSON Schema

Name	Required	Description
`json`	No	Return structured JSON for each URL in one step instead of page text. Pass a prompt, a JSON Schema, or both. Cannot be combined with objective.
`urls`	Yes	Exact public HTTP(S) resources to read. The router never substitutes another URL.
`_locus`	No	Optional Locus execution controls; provider arguments remain top-level.
`objective`	No	Optional focus within each supplied resource; it does not authorize discovery.
`maxCredits`	No	Aggregate hard charge ceiling in workspace credits. Decimal strings support up to six fractional digits; numeric values are rounded down to six digits.
`attribution`	No	Optional JSON ledger metadata such as a task or customer identifier.
`maxAgeSeconds`	No	Maximum accepted cache age. Omit to use each extractor default.
`externalUserId`	No	Optional end-user billing attribution for a tenant secret key.
`maxCharactersPerUrl`	No

Output Schema

TableJSON Schema

Name	Required	Description
`data`	Yes	Raw provider response.
`usd_charged`	No	USD charged (secret-key auth only).
`credits_balance`	No
`credits_charged`	No
`idempotent_replay`	No	Stored replay; no new charge.

Schema Changelog

Changes observed during successful MCP inspections.

Changed5 schema fields changedOct 7, 2026

addedInput schema / properties / json

Added value: +{
+  "additionalProperties": false,
+  "description": "Return structured JSON for each URL in one step instead of page text. Pass a prompt, a JSON Schema, or both. Cannot be combined with objective.",
+  "minProperties": 1,
+  "properties": {
+    "prompt": {
+      "maxLength": 400,
+      "minLength": 1,
+      "type": "string"
+    },
+    "schema": {
+      "additionalProperties": true,
+      "type": "object"
+    }
+  },
+  "type": "object"
+}

removedOutput schema / properties / credits_balance / description
```
Removed value: -"Remaining credit balance."
```
removedOutput schema / properties / credits_charged / description
```
Removed value: -"Credits debited for this call."
```

changedOutput schema / properties / data / description

Previous value: -"Raw upstream provider response body."New value: +"Raw provider response."

changedOutput schema / properties / idempotent_replay / description

Previous value: -"True when a stored identical call was replayed; no new charge was made."New value: +"Stored replay; no new charge."

AddedOct 3, 2026

TDQS

A4.1/5.0

Behavior4/5

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

Adds real behavioral context beyond annotations: 'Live billed request; the result reports credits charged' explains why readOnlyHint is false for a content read, and the two-stage extractor/retry story sets reliability expectations. It does not mention idempotency behavior or caching, though those are covered by schema parameters and 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?

Three tight sentences, front-loaded with the core action and scoping constraint, then the billing warning. No filler, though the extractor-retry sentence is closer to implementation detail than decision-relevant guidance.

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, return values needn't be described, and the description covers the key non-schema concerns: exact-URL-only scope, live billing, and credit reporting. It omits any mention of caching (maxAgeSeconds) or retry idempotency, which are minor given the schema's per-parameter docs.

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 89%, so the schema already documents urls, json, objective, maxCredits, maxAgeSeconds and the _locus controls in detail. The description adds only indirect meaning (cost is charged, no URL substitution) and no syntax or format guidance beyond the schema. Baseline 3 applies when the schema carries the parameter burden.

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?

States a specific verb (read/extract) and resource (the exact public URLs supplied by the caller), and explicitly contrasts its behavior with discovery ('never searches for substitutes'), which cleanly separates it from router_web_search and web_research without needing to name them.

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?

Gives a clear precondition (you must already have the exact URLs) and an implied exclusion (no search/substitution), so an agent knows this is not a discovery tool. It never names a concrete alternative tool for the discovery case, so the routing guidance stops just short of explicit.

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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