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

With no annotations, the description carries the full behavioral burden. It states that percent-encoding occurs, but does not explain mode-specific behavior, such as which reserved characters are preserved or encoded in component versus full URI mode, nor how spaces or delimiters are handled.

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 single sentence is front-loaded, free of filler, and appropriately sized for a simple two-parameter utility. Every clause contributes to identifying the tool and its main mode distinction.

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 primitive with no annotations and no output schema, the description is still too thin to let an agent choose the correct mode confidently. Mode semantics are the key missing context, and the schema does not provide them either.

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 0%, so the description must compensate. It repeats the mode enum values as 'component or full URI mode' but does not explain what each mode changes, and it adds no semantics for the input parameter beyond the obvious name.

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 gives a specific verb and resource: 'Percent-encode a string'. It also identifies two operational modes, component and full URI, making the tool clearly distinguishable from url_decode and other text transformation siblings.

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?

It mentions two modes parenthetically but gives no guidance on when to choose component versus full URI mode. There is no when-to-use context beyond the implied encoding operation, and no alternative or exclusion guidance.

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