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

Annotations already declare readOnly, idempotent, openWorld, non-destructive, so the safety profile is covered. The description adds genuinely new behavior: it is free but subject to a daily per-caller quota, and payment credentials must ride in MCP headers (X-Payment / X-Payment-Tx / Authorization: Bearer fg_…) rather than in arguments. That auth/quota detail is exactly the kind of context annotations cannot carry.

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 lead sentence is front-loaded and does the real work, but the block is padded: the free-tier fact is stated three times, the args-none fact twice, and the [zh]/[en] lines largely restate the opening. The pipe-separated first sentence is dense to the point of being hard to parse.

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 zero-parameter digest with no output schema, the description covers what will be returned (top pool score, medians, top-3 detail), cost/quota, and credential placement. Only the absence of routing to richer siblings and of response-size/format expectations keeps it below a 5.

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?

There are zero parameters, so the baseline is 4. The description corroborates the empty schema explicitly ('入参：无' / 'Args: none') and usefully clarifies that payment headers travel in the MCP request headers rather than as parameters, heading off a likely misuse.

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 the exact question the tool answers ('which stablecoin pool has the best risk adjusted yield') and enumerates the payload: highest smart_score pool, leaderboard APY/TVL medians, the Top20-vs-bottom score gap, and full scores for the top 3 pools. That is specific verb+resource+scope. It never names a sibling (top5, top20, by_chain, yield_methodology) to differentiate itself, 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?

Usage is implied through the question framing and the 'one-line call' / free-tier note, which tells an agent this is the cheap first-look entry point. There is no explicit when-not guidance and no routing to the sibling tools that provide per-chain breakdowns, full top-20 lists, or methodology details.

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