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

With no annotations at all, the description carries the full burden and does well: it discloses the exact return payload (outcomes, implied probabilities, 24h volume, liquidity/open interest, end date, link) and the ranking rule ('match then volume'). It also uniquely discloses a cost and payment mechanism — $0.003 USDC per call via x402 on Base — which is behavior an agent must know before calling. Missing rate limits, error behavior, and pagination semantics keep it short of a 5.

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 sentences: the capability and return shape first, the price second — front-loaded correctly with no filler. The first sentence is dense with a comma-list of returned fields, but each item supplies information the agent would otherwise lack given there is no output schema.

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 describe returns, and it does so thoroughly, including ranking and per-market fields. Payment terms are also covered. The remaining gap is operational detail — what happens on no matches, result pagination past 'limit', and failure modes — which is minor for a two-parameter read tool.

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%, with both q and limit documented including a range and default, so the schema already does the heavy lifting. The description adds only the notion of keyword matching and ranking order, not any syntax, quoting, or limit semantics beyond the schema.

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 ('Search open Polymarket and Kalshi markets by keywords') with the scope narrowed to open markets on two named venues, which separates it from a single-market lookup like odds_market. It never names the sibling tools (odds_market, odds_top) or states the boundary explicitly, so the differentiation is inferable 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?

Usage is only implied: the agent can infer keyword search is the entry point when it does not have a market identifier. There is no explicit 'use this when… / use odds_top instead when…' routing, and no guidance on query construction beyond the schema example.

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