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

Annotations already carry readOnly/idempotent/non-destructive, so the bar is lower, and the description clears it: it explains that returned values are DISPLAY prices (yes from best ask, no from 1 minus best bid), that they preserve the bid/ask spread, and that yes_price + no_price can exceed 1.0 without being a data error. That counterintuitive trait is exactly the kind of context an agent cannot get from structured fields.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

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

Front-loaded with purpose and return shape, and the display-price caveat earns its length. There is some duplication of the interval/fidelity semantics already in the schema, but overall it is dense and purposeful rather than padded.

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

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

There is no output schema, so the description must explain returns, and it does precisely (array of {timestamp, yes_price, no_price}) plus the interpretation caveat. It also points to the slug source. Nothing needed to call it correctly is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the baseline is 3. The description mostly restates the schema (interval choices, fidelity in minutes, default 60), adding only the mild framing that interval 'picks a fixed lookback window.' No new syntax or format detail beyond what the schema documents.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb+resource: historical Yes/No display-price time series for one Polymarket US market by slug. It names the input identity (slug) and the return shape, distinguishing it from siblings like polymarket_us_bbo (current book) and polymarket_us_search (lookup). The scope ('one market') is explicit.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

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

It tells the agent where to get the required slug ('from polymarket_us_search'), which is useful upstream routing. However, it never states when to prefer this over polymarket_us_bbo or other price/edge tools, nor any exclusion. Usage is implied by the 'historical' framing rather than spelled out.

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