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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, fully covering the safety and idempotence profile. The description adds no additional behavioral traits (e.g., supported range, handling of negatives, large numbers). Contributes minimal value beyond annotations.

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 a single sentence with an immediate purpose statement and an illustrative example. No extraneous words or fluff. Perfectly front-loaded and efficient.

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 simple tool with one parameter and good annotations, the description covers the core functionality with an example. Minor gaps: does not specify numeric range, behavior for zero or negative numbers, or output format for edge cases. Still, it is largely complete given the tool's simplicity. Missing output schema is acceptable as the return value is implicit from the example.

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% with a single parameter 'number' described as 'An integer.' The description adds an example but no further semantic detail or formatting constraints. Baseline score of 3 is appropriate as the schema does the heavy lifting.

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 clearly states the tool's function: 'Spell an integer in English words'. The example differentiates it from siblings like to_roman and convert_base by showing the English word output. It is specific and unambiguous.

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 converting numbers to words but does not explicitly state when to use it versus alternatives (e.g., to_roman, convert_base). No when-not guidance is provided. Usage is inferred from the example, but explicit guidance is missing.

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