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

Annotations already disclose that this is a safe, read-only, idempotent operation, so the description does not need to carry the full safety burden. It adds the default time window and sampling interval, but those defaults are also present in the schema, and it does not describe ordering, pagination behavior, or response shape.

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?

It is two tightly written sentences with the core purpose front-loaded, followed by a concrete usage example. There is no redundant or decorative language.

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 the rich schema and read-only annotations, the description provides enough to call the tool correctly for APY trend questions. Since there is no output schema, it could be slightly stronger by describing the snapshot return shape, but the core context is present.

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 all seven parameters are already well documented. The description's mention of the default 30-day window and daily interval reinforces the schema but adds no new parameter semantics, making the baseline 3 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?

The description states a specific verb and resource: get historical APY/reward rate snapshots for a yield over time. It clearly distinguishes this from sibling tools like yields_get_tvl_history by naming the exact data being returned and the question it answers.

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?

It gives clear usage context by naming the questions this tool answers (APY stability, APY trends) and states default behavior. It does not explicitly name a sibling alternative or when not to use it, which keeps it below a 5.

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