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

Annotations already declare readOnly, idempotent, open-world, non-destructive behavior, so the safety profile is covered. The description adds genuinely new context the annotations do not: the free daily allowance and the $0.001 USDC per-call x402 charge, which materially affects invocation decisions.

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: purpose first, cost second. Every clause earns its place with no redundancy or filler.

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?

An output schema exists, so return values need not be explained. The description covers what the tool returns and its cost model; the one gap is defining 'significant' (the USGS feed criterion) and how it relates to the overlapping m45-week sibling.

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 no parameter surface the description needs to compensate for. It neither adds nor omits anything meaningful here.

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 resource (significant earthquakes), a scope (worldwide), and a time window (past 7 days). It is clear on its own, but it does not differentiate itself from the sibling earthquakes__m45-week, which also covers a weekly window, leaving the agent to infer what 'significant' means versus a magnitude threshold.

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?

There is no when-to-use or when-not-to-use guidance and no reference to any of the five earthquake siblings (count, event, m25-day, m45-week, near). The only decision-relevant content is the pricing note, which is a cost signal rather than routing guidance.

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