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

The annotations already declare readOnlyHint=true, openWorldHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds useful behavioral context by clarifying that the response is lightweight, top-of-book only, and includes specific fields such as last trade price, bid/ask depth as number of price levels, open interest, shares traded, and market state. It stops short of operational details like rate limits or data latency.

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?

The description is front-loaded with the tool's purpose and scope, then immediately provides usage guidance, an alternative, and the slug source. The field list is lengthy but earns its place because there is no output schema to describe the return values.

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?

For a single-parameter read tool with no output schema and rich annotations, the description is complete enough to invoke correctly. It explains what is returned, when to use it, which sibling to choose instead for full depth, and where to obtain the required slug.

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 description coverage is 100%, and the single slug parameter is already well documented in the schema with an example and its source. The description reiterates that the tool operates by slug and that slugs come from polymarket_us_search, but it adds no syntax, format, or validation detail beyond the schema. A baseline 3 is appropriate when the schema carries the parameter semantics.

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?

The description names a specific read operation and resource: best bid/offer top-of-book for one Polymarket US market by slug. It also distinguishes this tool from its sibling by explicitly saying it is the lightweight top-of-book rather than the full depth ladder, so an agent can select it without opening another schema.

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 gives explicit when-to-use guidance ('Use before quoting a price when you need just the top of book'), an explicit when-not ('not the full depth ladder'), and names the alternative tool for the fuller view (polymarket_us_book). It also routes the agent to polymarket_us_search for obtaining a slug.

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