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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior, so the description's burden is reduced. It adds valuable details not in annotations: the $0.001 USDC cost per call and the supported chains. These enrich the agent's understanding of cost and applicability without contradicting any annotation.

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 two sentences long, front-loads the core function, and packs in cost and chain support without fluff. The example URL is somewhat lengthy but serves as a concrete reference. Every sentence adds value, though the example could be trimmed without losing essential info.

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?

Given that an output schema exists (return format is presumably handled there), the description adequately covers the tool's purpose, cost, supported chains, and the nature of the query. For a simple balance check, no critical usage details are missing. The only minor gap is the lack of explicit guidance on when to use this versus sibling NFT tools, but that's covered under usage guidelines.

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 schema covers all three parameters with descriptions, so the baseline is 3. The description adds the list of valid chain values (base, ethereum, arbitrum, bsc, polygon, optimism, avalanche) that the schema lacks (no enum), and provides a concrete example URL illustrating parameter usage. This meaningfully enhances parameter understanding beyond the schema.

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?

Clearly states it performs balanceOf(owner) on an NFT contract and returns the count of token IDs held by a wallet. Explicitly differentiates from other NFT tools by noting it avoids indexing every transfer, and the phrase 'how many ids one wallet holds' is precise. The tool name 'chain_nft_balance' is reinforced with concrete semantics.

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?

Provides context that it's a balance query and mentions efficiency ('without indexing every transfer'), but does not explicitly name alternative tools or state when to prefer this over siblings like chain_nft_owner or chain_nft_approved. The absence of explicit exclusions or alternative routing leaves some inference to the agent.

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