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

With no annotations provided, the description carries the full burden of behavioral disclosure. It adds only the vague phrase 'Expression discarded', which suggests some non-persistence but fails to explain what the tool returns, whether it mutates anything, or how it behaves on invalid input. This is too little context for an invocation decision.

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 short and the main verb is front-loaded, which is good for conciseness. However, the second sentence 'Expression discarded.' is structurally disconnected and ambiguous; it does not clearly earn its place and leaves the reader with more confusion 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?

This tool has seven input parameters and no output schema or annotations, yet the description does not explain which parameter holds the expression, what the return value is, or what 'discarded' means operationally. An agent has essentially no reliable way to invoke this tool correctly.

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 gives each of the seven parameters a description, so schema coverage is nominally high, but every parameter relates to refs, URLs, cities, feeds, hosts, JSON, or paths. The tool description promises arithmetic evaluation yet maps none of these parameters to an expression, so an agent cannot determine which argument to provide or whether the tool is usable at all. The description adds no parameter-level clarification and the schema does not compensate because it is mismatched.

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 does name a specific operation: 'Evaluate a+b style arithmetic', which gives a surface-level purpose and distinguishes it from the shape-checking siblings. However, the clause 'Expression discarded' is ambiguous about whether results are returned, and none of the seven input-schema properties can plausibly carry an arithmetic expression, making the stated purpose hard to act on.

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?

There is no guidance about when to use calc-eval instead of sibling tools, nor any mention of preconditions, alternatives, or exclusions. The description only states what the tool does in the abstract, leaving the agent to guess whether this is the right tool for a task.

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