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

The only behavioral claim is 'Expression discarded,' which suggests some input is not retained, but nothing is said about whether a numeric result is returned, how invalid expressions are handled, or what side effects occur, and no annotations are available to carry that burden. For an evaluation tool, this was not enough operational transparency.

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 very short and front-loaded with the primary action, which is structurally concise. However, the second sentence 'Expression discarded' creates ambiguity and the two sentences together do not compensate for the missing guidance, so the structure is compact but not especially effective.

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?

The tool has nine parameters, no annotations, and no output schema, so the description should not supply enough context to select and call it correctly. It does not explain the relationship between the schema and the 'arithmetic expression' claim, does not describe return behavior, and never clarifies which valid input to provide. This is a bare statement for a substantial service.

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?

All parameters have individual schema descriptions so the baseline is 3, but the top-level description does not link 'expression' to any of the nine properties, so an agent cannot determine which parameter corresponds to the arithmetic expression. The phrase 'a+b' suggests a parameter set that does not exist, making the description actively disconnected from the schema rather than helpful.

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 say 'Evaluate a+b style arithmetic,' which names a specific action and subject. However, the statement is vague because the schema exposes nine string properties and none of them represents an arithmetic expression, so an agent cannot see what input communicates 'a+b'. The appended 'Expression discarded' also clouds the purpose by suggesting the expression may not be used for computation.

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 this tool instead of any of the sibling tools, no prerequisites, and no indication whether it is for simple arithmetic checks or for any of the listed ref/url/city/feed/query shapes. Saying 'Expression discarded' gives a partial behavioral hint but does not guide an agent toward a correct invocation.

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