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

With no annotations, the description carries the full burden and discloses several non-obvious behaviors: the paid-per-call model with x402, pricing based on network caching, sharing mechanics, and that each answer includes the block at which it becomes invalid. It does not mention edge cases like what happens if there is no previous observation, but the disclosure is substantial.

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 concise and information-dense, covering purpose, examples, output, cost, and sharing in four sentences. It is front-loaded with the core purpose and avoids redundancy, though the opening question is largely rhetorical and could be trimmed.

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 the tool's simplicity (one parameter, no output schema), the description covers the key aspects: what it does, when to use it, what output to expect, and the business model. It lacks explicit failure/edge-case behavior, but for its complexity it is well-rounded and complete.

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 itself already provides a detailed description of the 'address' parameter, including its pattern and use case. The tool description reinforces that it refers to a 'Base contract' but adds little beyond the schema, so the baseline of 3 is appropriate.

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 description clearly states the tool's function: comparing a Base contract with its previous Tereno observation to detect changes such as proxy upgrades, admin swaps, bytecode changes, or pauses. It uses a specific verb ('compare') and resource ('Base contract', 'Tereno observation'), and the examples of detectable changes distinguish it from sibling tools like contract_guard or contract_interface.

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?

The description provides clear usage context by suggesting 'Poll it on a watchlist' and enumerating specific scenarios (silent proxy upgrade, admin swap, etc.). However, it does not explicitly mention when not to use this tool or name alternative tools, so it falls short of the highest mark.

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