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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so safety is covered. The description adds genuinely useful non-schema behavior: a free tier with a daily per-caller quota, a truncated top-3 result set, and the fact that payment/auth material goes in MCP headers (X-Payment, Bearer fg_…) rather than in parameters. It does not say what a caller sees when the quota is exhausted or whether limit actually changes the free-tier output.

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 core capability and the free-tier scope are front-loaded in the first sentence, which is good. However, the same content is restated three times across the plain, [zh] and [en] blocks, including a redundant 'limit、q' listing twice, and the payment-header note is buried at the end rather than grouped with the auth/quota context.

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 simple two-parameter read-only tool with no output schema, the definition covers purpose, quota and auth mechanics adequately. What it omits is the meaning of q and limit, which is the only thing an agent still has to guess at in order to invoke it correctly.

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?

The schema has 0% description coverage and the parameters are bare strings/numbers with only titles, so the description carries the burden. But it only says 'Args: limit, q' and repeats that both are optional, adding no meaning for q (keyword filter? query string?) or limit (max value, interaction with the fixed top-3 free tier). This is a real gap given zero schema coverage.

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 concrete behavior: returns the total market count plus the top 3 market titles with their Yes implied probability and 24h volume. That is a specific verb+resource, clearly a read/list operation. It does not explicitly contrast itself with the sibling prediction-odds.market_detail, so it stops short of a 5.

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?

Offers a usage trigger in the form of a natural-language question ('Ask "what are the prediction market odds"') and notes the free tier and daily per-caller quota, which implies the paid/extended path exists. It never names an alternative tool or states when not to use this one, so guidance is implied rather than explicit.

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