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

With no annotations, the description must fully disclose behavior, but it only says 'Expression discarded,' which is inconsistent with the schema (no expression exists). The actual behavior implied by the schema (e.g., 'discarded after the shape check') is not mentioned, so an agent would be misled about what the tool does and what happens to inputs.

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 extremely short (one sentence) and front-loaded with a misleading claim. While it is concise, it lacks any useful information and is not structured to help an agent understand the tool. Under-specification is not conciseness; this is unhelpfully brief.

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 tool with 9 parameters, no output schema, and no annotations, the description provides almost no contextual completeness. It fails to explain what the tool actually does, what inputs are for, what outputs to expect, or how it differs from siblings. An agent would have no basis to call it 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?

Schema description coverage is 100%, so the schema documents each parameter's purpose. However, the description adds no parameter-level meaning and instead misleads by referencing arithmetic that is absent from the schema. The baseline of 3 is reduced because the description actively conflicts with the parameter semantics, making it harder for an agent to correctly interpret the inputs.

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 claims the tool evaluates 'a+b style arithmetic,' but the input schema contains no arithmetic expression parameter; instead it has 9 unrelated string parameters (ref, url, city, feed, host, json, path, zone, query). This is actively misleading and fails to convey the tool's real function, which appears to be a shape-checker or validator given the sibling tools and schema descriptions.

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 on when to use this tool versus alternatives. The description provides no context, no exclusions, and no mention of any specific use case that would distinguish it from the many sibling tools like domain-shape or validate-json.

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