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

Annotations already declare readOnly/destructive=false, so the safety profile is covered. The description adds meaningful context beyond them: it is a 'cheap tier' call, returns live data, and is 'Paid in USDC on Base' (cost/payment model). Return format is not described, but an output schema exists.

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-loads the cheap-tier/purpose, then the exclusion routing, then input mechanics. Dense but every clause earns its place with no redundancy.

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 read-only priced metric with full schema coverage, an output schema, and annotations covering safety, nothing an agent needs to invoke it correctly is missing: scope, routing, input form, and payment are all stated.

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 baseline is 3. The description adds real meaning beyond the schema: the either/or resolution logic (raw token_id OR market_slug+outcome) and the 'exact slug only, no fuzzy keyword search' constraint on market_slug.

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+scope: a single Polymarket outcome's live top-of-book bid/ask spread as a percentage of mid_price. It is precisely distinguishable from siblings like orderbook_imbalance_ratio or liquidity tools.

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?

Explicitly says what it is NOT ('Not a liquidity or executability measure') and names the alternatives (prediction.exit_capacity_audit/order_split_guide). Adds the exact-slug-only constraint, so the agent knows not to attempt fuzzy search.

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