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

With no annotations, the description carries the full burden, and it delivers meaningful traits: engines are deterministic and offline (implying no side effects), they validate input, and a wrong unit surfaces as an error rather than being silently absorbed. This is exactly the kind of behavioral context an agent needs to trust the output. It stops short of stating permissions, side effects explicitly, or the shape of error responses.

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?

Three tight sentences, front-loaded with the primary action and verdict, followed by the optional-input behavior and a behavioral caveat. Every sentence earns its place with no filler.

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?

There is no output schema and no annotations, so the description should carry more of the return/error burden. 'Return its verdict' plus the error-on-wrong-unit note hints at the response, but the verdict's structure and the error shape are undefined, leaving a gap for a tool whose entire purpose is producing output.

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%, so both parameters are already documented, including that `input` may be an object or a named mode string. The description largely restates this ('Pass `input` as an object of the engine's fields', 'Omit `input`...') with little added syntax or format detail, so the baseline of 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 and resource: 'Run an AAJ engine and return its verdict.' The agent knows this executes an engine and produces a result, which is clearly distinct from list_engines/describe_engine by implication. However, the description itself never names the sibling tools, so the differentiation must be inferred from the schema's mention of 'list_engines' and 'describe_engine'.

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 clear in-tool guidance for the two modes of `input` (provide config vs omit for the built-in worked example), which is genuinely useful. But it offers no explicit when-to-use guidance relative to alternatives like describe_engine (to learn an engine's modes) or list_engines (to discover ids), leaving the agent to infer the workflow.

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