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

Annotations already declare readOnly/idempotent=false, and the description goes well beyond them: it explains partial-failure semantics (a non-responding network is reported as an error entry rather than failing the whole call), states the billing model and free tier, and explains why repeats are not free — which directly accounts for idempotentHint=false. It also restates the no-side-effects guarantee in operational terms.

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 purpose and network scope are front-loaded, and structure moves cleanly from what it returns to when to use it to cost. The only waste is mild redundancy between the cost sentence and the closing 'each call is charged, so repeats are not free', which partially restates the pricing clause.

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?

With no output schema, the description still tells the agent what comes back (per-network figures, per-token sums, a grand total), how failures surface, and what the call costs. For a one-parameter read-only aggregation tool this is everything needed to invoke 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 coverage is 100% and the single 'token' parameter already documents the USDC/USDT/both options and the 'both' default. The description's example (token=both) merely illustrates a value the schema already defines, adding no new semantics such as case sensitivity or invalid-value behavior.

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 first sentence names the exact resource (total supply of USDC and USDT), the exact scope (five named networks), the data source (each token contract's totalSupply) and the aggregation shape (per network, per token, grand total). This is clearly distinct from the per-chain siblings like polygon_token_info or eth_token_balance, which return token metadata or a single wallet's balance rather than an issuance aggregate.

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?

It gives concrete use cases — tracking issuance, chain liquidity, mints and burns over time — plus a worked example (token=both), which is enough for an agent to know when this is the right tool. It does not, however, name an alternative or state when not to use it (e.g. for a single wallet's USDC balance use polygon_token_balance), so it stops short of explicit routing.

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