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

Adds genuinely non-obvious behavior beyond the annotations: malformed address/slot returns 400 and is uncharged, pricing is $0.01/call with the first 25 free and failed calls free, and each repeat call is billed. That last point explains the otherwise puzzling idempotentHint=false on a pure read, which the annotations alone would not convey.

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?

Front-loads the operation and the return shape, then routes to the alternative and closes with error/pricing facts. Dense and mostly waste-free, though the charging point is restated ('first 25 free; failed calls free' then 'each call is charged, so repeats are not free').

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 two-parameter read tool with no output schema, the description still explains what comes back (number and optional address decoding), what errors to expect, and cost implications. Nothing an agent needs to call it correctly is absent.

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 already 100%, but the description adds meaning the schema does not: that the slot argument accepts mapping and proxy slots and that the address form is a 0x 32-byte key, plus a worked address example. Marginal but real value over the structured fields.

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 verb and resource ('read one raw storage slot ... eth_getStorageAt') and details the return form (32-byte word as number, and as address when applicable). It explicitly distinguishes itself from the sibling polygon_proxy, so an agent can pick between them without opening a schema.

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?

Gives a concrete use case ('inspect contract state that has no getter, owners or implementation pointers') and names the alternative for proxy slots (polygon_proxy). The inverse case - use polygon_call for state that does have a getter - is only implied, so not quite a full when/when-not/alternatives statement.

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