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

Annotations only cover the read-only/idempotent safety profile, but the description adds substantial behavioral context: the URI is capped text and never fetched, returned strings are attacker-controlled and must be treated as untrusted data rather than instructions, malformed node answers surface as 5xx and are not charged, and typical latency is 0.3-2 s. That security and billing disclosure goes well beyond the annotations.

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-loaded with purpose and the sibling routing, then security, then cost/latency. Dense but nearly every clause carries operational value; the pricing, free-tier and docs sentences are warranted for a paid metered tool, though the block reads more like a listing than a crisp description.

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?

An output schema exists, so return values need not be explained. Given that, the description covers chains, sibling routing, trust model for returned strings, failure semantics, latency and price — everything an agent needs to select and safely invoke it.

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%: chain enum, the 0x+40-hex contract pattern, and the token-id decimal/hex format are all documented in the schema. The description adds no further parameter-level meaning, so the 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?

States a specific verb+resource ('read one NFT') plus the supported chains, and directly names the sibling get_nft_owner with the scope that distinguishes them (owner only vs. standard + owner + token URI). An agent can route between the two without opening either 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?

Explicitly gives the when-to-use-this vs. when-to-use-the-alternative rule: 'For the ERC-721 owner alone use get_nft_owner.' It also bounds the tool to three named chains and states the free-tier quota, so an agent knows both the substitution case and the cost context.

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