Plans and limits

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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered. The description adds genuinely new behavioral context the annotations do not: that no API key/authentication is required. It stops short of saying whether the data is static or cached.

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?

Two short sentences with zero filler, and the most decision-relevant fact (what you get) is front-loaded before the auth note. Every clause 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 zero-parameter, read-only public endpoint with no output schema, the description conveys enough to call it correctly and to know what the payload covers. Minor gap: it does not say how the tier data is structured or whether it changes over time.

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 tool takes zero parameters, so the baseline is 4; there is nothing the description needs to disambiguate, and schema coverage is 100%.

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?

Names the specific resource (public plans) and enumerates the fields returned: price, history cap, request limits and size. That is enough to distinguish it from siblings like tilla_usage or tilla_status, though it never states a verb ("returns" / "lists") and never explicitly contrasts with those siblings.

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?

"No API key needed" implies this is a safe, unauthenticated call an agent can make up front, but there is no explicit when-to-use or when-not-to-use guidance and no routing to alternatives such as tilla_usage or tilla_about. Usage is inferable rather than stated.

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