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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds genuinely useful behavior beyond the annotations: it is a pure calculation with no side effects and it enumerates what comes back (fee, net amount, formatted versions), which matters since no output schema exists.

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 tight sentences: what it computes first, then when to use it. Minor redundancy with the schema on units, but nothing is wasted.

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 single-parameter read-only calculator with no output schema, the description covers the computation, the units, the return shape, and the intended usage. It leaves open the fee rate/basis, but an agent has enough to call it correctly.

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%, and the schema already documents the BigInt string and the 6-decimal example. The description restates "6-decimal units" without adding format or edge-case detail, so baseline 3 applies.

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?

Specific verb+resource: it calculates the protocol fee for a USDC amount and states the units (6-decimal). However, it does not distinguish itself from close siblings like protocol_escrow_fees, protocol_token_fees, or pcc_protocol_fee, so an agent cannot route between fee tools from this description alone.

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?

"Use this before building escrow contracts to understand the true cost" gives a clear usage context and sequencing cue. It stops short of naming alternatives or stating when another fee tool would be the right pick, so it lacks exclusions.

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