Cook County / Chicago Property Data (free tier, no wallet needed)

Chicago comparable sales / AVM (100 free a day)

find_chicago_comparable_sales

Read-onlyIdempotent

FREE for your first 100 calls each day — no wallet, no signup, just call it ($0.10 per call via x402/USDC only after that daily allowance, which resets at 00:00 UTC). Recent arm's-length comparable sales (comps) in the same Cook County assessor neighborhood and property class as the given PIN, each with its distance in metres from the subject, plus an implied low/median/high price range — a derived, lightweight automated valuation (AVM) you won't get from a raw open-data query. Thin markets widen automatically and the response reports which matching rung was used. Comps are NOT normalized for building size or age.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "pin": "<pin>"
    },
    "name": "find_chicago_comparable_sales"
  }
}

Input Schema

Name	Required	Description	Default
`pin`	Yes	10- or 14-digit Cook County PIN (digits; dashes allowed, e.g. 09-25-306-051-0000). If you only have a street address, call search_chicago_property_by_address first.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 16, 2026

changedInput schema / properties / pin / description

Previous value: -"10- or 14-digit Cook County PIN (digits; dashes allowed, e.g. 14-08-120-017-0000). If you only have a street address, call search_chicago_property_by_address first."New value: +"10- or 14-digit Cook County PIN (digits; dashes allowed, e.g. 09-25-306-051-0000). If you only have a street address, call search_chicago_property_by_address first."

Changed1 schema field changedJul 16, 2026
- changedInput schema / properties / pin / pattern
```
Previous value: -"^[0-9][0-9\\-]{8,17}$"New value: +"^[0-9][0-9\\-]{8,19}$"
```

Changed2 schema fields changedJul 12, 2026

addedInput schema / properties / pin / description

Added value: +"10- or 14-digit Cook County PIN (digits; dashes allowed, e.g. 14-08-120-017-0000). If you only have a street address, call search_chicago_property_by_address first."

addedInput schema / properties / pin / pattern
```
Added value: +"^[0-9][0-9\\-]{8,17}$"
```

First observedJun 28, 2026

TDQS

A4.4/5.0

Behavior5/5

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

Annotations already cover readOnly/idempotent/non-destructive/openWorld, and the description still adds substantial behavioral detail: the rate-limit/pricing model and reset window, that thin markets widen the match automatically, that the response reports which matching rung was used, and the important caveat that comps are NOT normalized for building size or age.

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?

Front-loads the free-allowance hook, then moves to what the tool returns and its limits. Every sentence carries content, though the pricing clause is somewhat long for a description whose primary job is tool selection.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

No output schema exists, and the description compensates by explaining the return shape (comps with distance in metres, implied low/median/high range, which matching rung was used) together with the key statistical caveat. An agent has everything needed to call and interpret it.

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 coverage is 100% and there is only one parameter whose schema description already explains the PIN format and the address routing. The description adds no further parameter-level meaning, so the baseline 3 applies.

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+resource+scope: arm's-length comparable sales in the same Cook County assessor neighborhood and property class as the given PIN, plus an implied low/median/high AVM range. It explicitly differentiates itself from siblings by noting this is a derived valuation 'you won't get from a raw open-data query' (e.g., get_cook_county_parcel).

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 clear operational context — first 100 calls/day free with no signup, $0.10/call via x402/USDC after, resetting 00:00 UTC. It does not, however, explicitly say when to prefer this over get_cook_county_property_dossier or the other siblings; the schema (not the description) carries the address-vs-PIN routing hint.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

All Cook County / Chicago Property Data (free tier, no wallet needed) tools Inspect

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