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

Annotations are absent, so the description carries the full burden — and it delivers: it front-loads that the tool is paid, specifies pricing per call in USDC on three chains, and discloses both payment paths (x402 or Bearer bby_live_... header for prepaid credits). For a tool with zero annotation coverage, this is strong behavioral disclosure. It loses a point for not addressing failure behavior, rate limits, or what happens on invalid payment, but the cost/auth essentials are unusually well covered.

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?

Four short sentences, each earning its place: purpose and paid status are front-loaded, invocation follows, payment mechanics next, and routing guidance closes. There is zero filler and the most decision-relevant information (cost, generic scope) appears first.

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 generic proxy to arbitrary endpoints, response format is inherently endpoint-specific, so the absence of return-value documentation is excusable. The description covers cost, invocation, and parameter discovery via describe_endpoint. Minor gaps: it never states that the raw endpoint response is returned, nor error handling for failed payments or bad paths — but for a tool this open-ended, the coverage is solid.

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%: both path and params already have meaningful schema descriptions with examples. The description's 'path and query parameters together in params' note slightly reinforces the schema's statement but adds little new semantic information. Baseline 3 applies because the schema does the heavy lifting.

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 states a specific verb and resource: 'Fetch live data from any fetcher.sh endpoint.' This clearly identifies it as a generic dispatch/proxy tool for arbitrary endpoints, which distinguishes it from its siblings (search_endpoints finds endpoints, describe_endpoint describes them, check_balance and topup_credits handle billing). The scope and role are unmistakable.

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 description gives explicit routing guidance: 'Call describe_endpoint first if unsure about parameters' and 'For a named tool per endpoint, use [service].fetcher.sh/mcp.' Together with the schema's reference to search_endpoints as the path source, an agent knows exactly which sibling to use when. The when-not guidance for fetch_data (use a named tool) is stated directly.

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