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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered; the description adds real value beyond that by naming the data source (indexer only), which implies freshness/coverage limits, and by disclosing the paid-call model ($0.002 USDC via x402, failures not charged). It does not mention rate limits, pagination, or what happens when a ticker is unknown, which would be the remaining gaps.

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 resource and its return fields, then caveats, routing, and pricing in descending priority — a sensible order. The sibling-routing clause is somewhat verbose boilerplate for two unrelated tools, but no sentence is truly wasted.

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 an output schema present, the descriptive field list is bonus rather than obligation, and the definition still covers data source, cost model, and scope. An agent has everything needed to decide to call it and to invoke it correctly with a single ticker.

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?

One parameter at 100% schema description coverage, and the schema already gives format examples (BTC-USD, ETH-USD). The description only reinforces the single-ticker scope; it adds no new meaning such as case sensitivity, whether the ticker must be a listed dYdX market, or fallback behaviour. 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 resource (dYdX v4 perpetual market for one ticker) and enumerates exactly what is returned: status, oracle price, 24h change/volume/trade count, hourly funding, margin requirements, open interest in base units and USD. An agent can distinguish this from the many other crypto market tools without opening the 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?

Explicitly scopes the tool to a single-ticker perp lookup and routes two other needs to named siblings (crypto_aave_lending_markets, crypto_btc_chain_tips) with the condition for each. The gap is that the routing targets are distant domains while the closest neighbours (crypto_hyperliquid_perps_depth, finance_hyperliquid_perp_funding) are never mentioned, so an agent choosing between perp sources gets no guidance.

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