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

Annotations already provide readOnlyHint and openWorldHint. The description adds valuable behavioral context: the paid nature ($0.005 USDC via x402), per-ID data enrichment, and derived metrics (momentum score, signal, volatility flag). This goes beyond what annotations convey.

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?

A single dense sentence front-loads the most critical constraint (paid) and enumerates all returned fields. Every clause adds value, with no fluff or redundancy.

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?

With no output schema, the description enumerates all key return values (price, market cap, 24h change/volume, momentum score, signal, volatility flag) and explains the payment mechanism. Minor omissions like response format or error handling, but sufficient for an agent to select and invoke 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?

Schema coverage is 100%, so the baseline is 3. The description reinforces that 'ids' are CoinGecko IDs and mentions the payment context for x402_payment, but it does not add details beyond what the input schema already documents.

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 clearly states the tool returns price, market cap, 24h change, 24h volume, momentum score, signal, and volatility flag for each CoinGecko ID. This specific verb+resource combination easily distinguishes it from sibling tools like agent_web_reader and github_repo_seo_audit.

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?

Explicitly frames the tool for use in a trading/research loop and mentions the payment challenge if x402_payment is omitted. It does not name alternative tools or explicit when-not conditions, but the context is clear and sufficient given the unrelated siblings.

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