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

With no annotations, the description carries the full behavioral burden. It only discloses that the expression is discarded; it does not say what the tool returns, whether any of the nine schema inputs are used, or what side effects occur. The mention of an expression with no corresponding schema parameter is an unexplained behavioral gap.

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 purpose appears first, but the second sentence 'Expression discarded' is confusing and not self-contained because there is no expression field. It is concise in word count, but not in 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?

For a 9-parameter tool with no annotations and no output schema, this is far from complete. It does not specify how to pass the arithmetic expression, what output to expect, or when the tool should be selected, so an agent lacks essential invocation information.

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?

Every schema parameter already has a description, so the baseline is 3. The tool description adds no parameter-level meaning and, worse, refers to an 'expression' that does not exist in the schema, so an agent cannot map the described input to a concrete field. However, the schema itself fully documents its own nine parameters.

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 phrase 'Evaluate a+b style arithmetic' names a specific verb and object, so it is not a tautology. However, the schema exposes no expression parameter at all; the nine inputs are ref, url, city, feed, host, json, path, and query. This leaves the actual purpose ambiguous and does not differentiate the tool from sibling validators such as validate-json.

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?

No when-to-use or when-not-to-use guidance is provided. The description never references alternatives like web-fetch or validate-json, and gives no context for when calc-eval is the right tool versus any sibling.

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