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

With no annotations, the description carries the full burden and delivers: it discloses the 2-live-quote minimum, that unlisted tickers are not charged, the free tier's unsigned/rate-limited nature, and the x402 payment mechanics with exact header names and cost. This is unusually rich behavioral detail for a tool with zero annotation coverage.

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-loaded with the core purpose and usage triggers, and the pricing/transport details follow logically. It is dense but every sentence (exchange list, spread/flag output, quote minimum, free-vs-paid, headers) serves a decision. Slightly long, keeping it from a 5.

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?

Comprehensive for a single-param tool with no output schema: it explains the return shape (median, spread, divergence flag, attestation), the preconditions (two live quotes), failure/billing behavior (unlisted ticker not charged), and both free/paid access paths. Nothing an agent needs to call it correctly is missing.

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% (the single 'symbol' param is fully described with examples), so the schema already does the heavy lifting. The description adds the accepted ticker set (BTC, ETH, SOL, or any ticker), which is mildly helpful context, but no syntax beyond the schema. Baseline 3 is appropriate.

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 (spot crypto price check for a token ticker in USD) and adds concrete scope: cross-checked across five named exchanges, returning a median, spread, and divergence flag. An agent can distinguish this from the verify_* siblings (business, claim, freshness) without opening any schema.

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?

Explicit triggers are listed: 'Use it before your agent trades, quotes, values a portfolio or settles on a token price.' The alternatives/paths are also named (free unsigned tier vs. paid signed attestation via payment header or HTTP POST), giving the agent a clear when-and-how decision.

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