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

No annotations are provided, so the description carries the full behavioral burden. It discloses one negative behavior (no browser launch) but does not explain what 'check' actually does—whether it makes a network request, validates URL syntax, or what side effects might occur. The schema parameters mentioning 'discarded after the shape check' and 'discarded after the call' hint at broader behaviors not covered in the description.

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 consists of two tight, front-loaded sentences. The core action ('Check whether a URL can be opened') and the critical scoping qualifier ('No browser is launched') both earn their place with no superfluous words.

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?

With no output schema and no annotations, the description alone must cover the tool's scope. It addresses only the URL check, yet the input schema includes 7 heterogeneous parameters (ref, city, feed, json, path, host) whose descriptions imply multiple distinct operations. An agent would not know the tool can validate JSON, provide weather hints, or handle shapes beyond URLs, leaving the description incomplete for the full tool behavior.

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?

All 7 parameters have descriptions in the schema, yielding 100% schema_description_coverage. The tool description adds no parameter-specific meaning and only generically references URL. With high schema coverage, the baseline of 3 is appropriate; the description neither compensates nor detracts.

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 states a specific verb ('Check') and resource ('URL'), and the clause 'No browser is launched' actively distinguishes it from browser-launching siblings like playwright-url-ok. The agent can immediately tell this is a lightweight URL check rather than a fetch or browser automation 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 intended use case: checking URL openability without launching a browser. However, it does not explicitly name alternatives or give when-not-to-use criteria. The contrast with browser-launching tools is present but subtle, so the guidance is implied rather than explicit.

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