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

With no annotations, the description must disclose behavior itself. The only behavioral trait stated is that the expression is discarded, but the description says nothing about return values, error handling, side effects, or auth. Worse, the schema's per-field 'discarded after...' notes suggest a different generic discard behavior, and the expression input is never located.

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 two short sentences with no filler and the core verb is front-loaded. However, extreme brevity borders on under-specification, which slightly lowers the score.

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 nine optional parameters, no annotations, and no output schema, a six-word description does not enable correct invocation. It lacks the input-to-expression mapping, return format, and any details about how the expression is supplied.

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 coverage is 100%, so the schema documents each field, but the description adds no mapping from 'a+b' to any of the nine parameters. Since all parameters are optional and no expression field exists, an agent cannot determine what to pass for arithmetic evaluation.

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 names a specific operation, evaluating a+b arithmetic, and notes the expression is discarded. However, the input schema contains no expression parameter—only ref, url, city, feed, host, json, path, zone, and query—so the stated purpose does not map to any caller-visible input. This makes the purpose misleading for an agent trying to invoke the tool.

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 implies the tool is for arithmetic evaluation but gives no guidance on when to choose calc-eval over siblings such as validate-json or search-query-len. It also provides no exclusions, prerequisites, or situational rules.

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