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

With no annotations, the description carries the full burden and does disclose the safety profile ('Read-only market data') plus the opt-in enrichment behavior of includeBook (best bid/ask, spread, top 5 order-book levels per outcome). It stops short of error/unfound behavior and rate or auth considerations.

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?

Two front-loaded sentences with no redundancy; the lookup key and the optional enrichment are stated immediately. The trailing 'not financial advice' disclaimer is marginally useful context rather than a functional statement.

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-item read tool with no output schema, the description covers the inputs it needs to resolve (slug or id), the read-only nature, and the shape of the enriched payload. It omits what happens when neither identifier resolves or both are supplied, a minor gap given zero required parameters.

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 0%, so the description must compensate: it identifies both lookup keys (slug/id) and, crucially, explains what the includeBook flag actually adds (bid/ask, spread, order-book depth), which the bare boolean schema cannot convey. The regex/length constraints on id and slug remain undocumented in prose.

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 and resource ('Fetches one Polymarket market') and the lookup keys (slug or id), which makes it clearly distinguishable in intent from a bulk search_markets. It does not name the sibling explicitly, so the differentiation is implied rather than stated.

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?

The phrase 'one Polymarket market by slug or id' implies the usage context (when you already have a specific market identifier), but there is no explicit when-to-use vs. when-to-use search_markets guidance and no stated prerequisites or failure conditions.

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