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

With no annotations, the description bears the full burden of behavioral disclosure. It says 'Evaluate' but then 'Expression discarded,' which is contradictory and unclear—does it compute and return, or simply validate and return nothing? No details on side effects, return format, or side effects are given.

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 a single sentence, which is concise, but it is so under-specified that it is effectively incomplete. There is no structure, no key information front-loaded, and the phrase 'Expression discarded' adds confusion rather than clarity.

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 9 parameters, no annotations, no output schema, and no usage guidance, this description is grossly inadequate. It does not explain what the tool returns, how parameters are used, what 'discarded' means, or any constraints. An agent would have to guess the tool's behavior, which is unacceptable.

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?

Although schema description coverage is 100%, the description itself adds no meaning to the parameters. Worse, it explicitly claims an arithmetic operation while all parameters are URLs, file paths, city names, etc., creating a conflict. The description does not explain how these parameters relate to 'a+b' arithmetic, leaving the agent with no clue how to populate them.

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 'Evaluate a+b style arithmetic' gives a verb and resource, suggesting a simple arithmetic evaluator. However, the input schema contains 9 parameters (url, city, feed, host, json, path, zone, query, etc.) that have nothing to do with arithmetic, making the purpose confusing and misleading. It fails to clearly distinguish itself from siblings, as no sibling appears arithmetic-related.

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 no guidance on when to use this tool versus alternatives. There is no mention of context, exclusions, or relationships to sibling tools. The cryptic 'Expression discarded' hints at a validation-only role but not when to invoke it.

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