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

Annotations already declare readOnlyHint=true and destructiveHint=false, and the description adds meaningful behavior beyond that: it performs a pure calculation on top of funding_rate data, has no extra upstream call, flags the funding-paying side, and is paid in USDC on Base. These details are not visible elsewhere.

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?

Three dense, front-loaded sentences cover the main action, exclusions, alternatives, and payment context with zero filler. Every sentence earns its place.

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 two-parameter calculation tool with an output schema, the description covers purpose, usage boundaries, computation behavior, and payment context. Nothing needed for correct invocation 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 description coverage is 100%, so the schema already fully documents both parameters. The description contextualizes assumed_round_trip_cost_pct as the cost recouped by funding income, but it does not add new parameter-level details beyond what the schema already provides.

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: 'evaluate a spot+perpetual carry trade' and enumerates three concrete outputs: annualized APR, funding side, and days to recoup cost. It also explicitly distinguishes itself from the sibling tool derivatives.funding_rate, making its purpose clear without needing to open schemas.

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?

Contains explicit routing guidance: 'Do not use for the raw current funding rate alone (use derivatives.funding_rate) or for spot price data.' It also clarifies this is a pure calculation with no extra upstream call, which tells the agent exactly when this tool is appropriate versus alternatives.

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