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

Annotations already cover readOnly/idempotent/openWorld, but the description adds substantial behavioral context beyond them: 422 (unbilled) for unsupported pairs, latency 0.2-1 s, USD 0.002 cost, a shared 10-reads/IP/day free pool, and an untrusted-data warning about page/on-chain strings.

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?

Dense and front-loaded with the core read action, then inputs, return fields, failure mode, timing and cost. It is long and somewhat run-on, but nearly every clause carries operational information an agent needs.

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 the returned fields (price as exact decimal string, decimals, round_id, updated_at, age_seconds, stale with heartbeat rule, feed address), plus error and cost behavior. An agent has everything needed to call and interpret the result.

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, but the description adds meaning the schema does not: which pairs are valid on ethereum vs base, and that chains are limited to ethereum|base. The enum values themselves are already in the schema.

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 ('read a token price from a Chainlink on-chain price feed') and explicitly distinguishes itself from the DEX-spot-price approach used by siblings like get_swap_quote. An agent can tell what this returns 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?

The framing as a 'deterministic oracle answer, not a DEX spot price' implicitly routes the agent away from spot-quote siblings, and the free-tier/pricing context helps decide when to call. However, it never states an explicit 'use this instead of X when...' condition, so the guidance is context rather than a rule.

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