Url Word Stats

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint false. The description adds that it does not execute JavaScript and does not bypass access controls, which provides safety reassurance beyond annotations. The use of 'Estimate' indicates approximate results.

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?

Three sentences with no wasted words: first sentence states purpose and outputs, second gives constraints and capabilities, third gives parameter-specific guidance. Maximum information density.

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?

Given the simple tool (two parameters, one required), the description covers essential aspects: what it does, when to use it, limitations, and parameter usage. Since an output schema exists, no need to describe return values. Slightly incomplete on error scenarios or rate limits, but adequate for the tool's simplicity.

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?

Both parameters are fully described in the schema (100% coverage). The description reiterates usage for 'url' ('absolute public HTTP(S) URL') and adds operational guidance for 'fresh' ('allow cache reuse' vs 'require new upstream fetch'), adding practical context without redundancy.

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 starts with a clear, specific verb ('Estimate') and lists the exact outputs (words, characters, sentences, reading time). It immediately distinguishes itself from sibling URL analysis tools like url_text or url_extract by focusing on estimation metrics.

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?

Explicitly states the tool is for public HTTP(S) resources only, does not execute JavaScript or bypass access controls, and provides clear caching guidance ('keep fresh=false to allow cache reuse; set fresh=true only when a new upstream fetch is required'). While it doesn't explicitly compare to alternatives, the context is well-defined.

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