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

Annotations already declare readOnlyHint=true, idempotentHint=true, and openWorldHint=false, covering the safety profile. The description adds one genuinely useful behavioral fact: processing runs locally in the browser and nothing is uploaded, which is not derivable from the annotations. It says nothing about output format or limitations beyond the 100k maxLength, which is in the schema.

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?

Two short sentences: the first front-loads the transformation and modes, the second adds the privacy guarantee; the URL is extra but harmless. No filler or repetition, though the trailing link is not meaningful to an agent.

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 two-parameter, zero-required, read-only text tool with full schema coverage, the basics are covered. However, with no output schema, the description never states what the tool returns (converted text? object?), and it omits which mode to choose when none is given beyond relying on the default. Adequate but with clear gaps.

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 enum values and text parameter are already documented in the schema; the description merely restates the same modes. Baseline 3 applies when the schema does the heavy lifting and the description adds little beyond it.

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?

States a specific verb ('Switch text') and enumerates the concrete output modes, so an agent knows exactly what transformations are offered. The name and mode enum corroborate it. It doesn't explicitly distinguish itself from nearby text tools like word_counter, and the sibling list mostly contains calculators, so differentiation is implicit rather than stated.

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, nor any conditions or exclusions. The default mode is 'title' (also the assumed default in the description ordering) but the description never tells the agent which mode to pick for a given intent. Usage context is entirely left to inference.

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