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

Beyond the readOnly and idempotent annotations, the description discloses a $0.10 USDC charge per call, an approximate row count for AWS regions, and per-row timestamp/age fields. It also specifies that semantics match /spot/latest, giving the agent useful operational context before invoking.

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 dense and front-loaded with the cost and scope. The final sentence about being priced higher partially repeats the opening payment note, but it earns its place by explaining the trade-off versus a narrower snapshot.

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?

Even with no output schema, the description covers the return shape: rows, timestamps, age, and approximate count. It gives enough context for an agent to know what it will receive and why the call costs more, though the term 'series' is not fully defined.

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%: both provider and region have descriptions and provider has an enum. The description adds no extra parameter-level meaning, so the baseline of 3 is 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 clearly identifies a whole-region bulk snapshot of current spot prices across all instance types, zones, and products, and it distinguishes itself by scale and cost. The verb is implicit rather than explicit, but the resource and scope are concrete enough to separate it from siblings like spot_latest.

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 states the primary use case: get the entire current price surface of a region in one call. Referencing /spot/latest and the higher price implies the alternative for narrower queries, though it stops short of explicitly saying 'use spot_latest for a single series or when cost matters more.'

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