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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false. The description goes further by explaining the tool calls latestRoundData on the feed contract itself, which eliminates API vendor/rate limit/key concerns, and it includes staleness metrics (updatedAt, ageSeconds) so the agent can judge data freshness. No contradictions with annotations.

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?

The description is long but every section earns its place: intro, mechanism, named pairs, usage guidance, parameters, return structure. It is front-loaded with purpose and structured into scannable paragraphs. There is no filler or redundant restating of the tool name.

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?

Given there is no output schema, the description provides a detailed return example with field names and types, including staleness measures. It also covers the supported chains and the distinction between named pairs and raw addresses. Limitations (no historical prices) are stated. This is complete for an agent to use 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?

The input schema descriptions cover both parameters (pair and chain) at 100% coverage, so the baseline is 3. The description adds examples ('ETH/USD', 0x...) and notes that any feed address on supported chains works, but the schema already conveys the core semantics. No additional parameter behavior is introduced beyond what the schema fields express.

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 opens with a specific verb-resource combination: 'Read any Chainlink price feed directly on-chain'. It clearly differentiates itself from sibling tools like onchain_portfolio and onchain_gas by targeting Chainlink oracle prices specifically, and gives the exact mechanism (latestRoundData on the feed contract).

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 description has explicit 'When to use' and 'When NOT to use' sections. It names alternatives (onchain_portfolio or DEX quote when no Chainlink feed exists) and explicitly excludes historical/point-in-time prices. This is exactly the kind of clear guidance an agent needs.

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