Type

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

Goes beyond the annotations by disclosing two real behaviors: "submit presses Enter after" changes what the call does, and "Answers with what changed on screen, not a new snapshot" tells the agent the return is a diff and that a separate snapshot is needed for full state. Annotations only give the generic readOnly=false/openWorld=true profile, so this added context matters.

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?

One front-loaded sentence carrying the action first, then alternatives, then return behavior — no wasted clauses. The semicolon-chained style is dense to the point of being telegraphic, which costs a little readability.

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 3-param tool with no output schema, it covers the essentials: what is replaced, what submit does, where to go for dropdowns/keys, and what the response represents. Only minor gaps remain (frame/ref sourcing is left to the schema, no mention of failure modes on non-editable targets).

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 ref, text and submit are already fully documented, including "the field's whole new text" and "press Enter after; default false." The description restates the same facts (replace whole text, submit presses Enter) without adding new semantics, so baseline 3 applies.

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 and resource ("Replace the text of a field or editable area by its ref") and immediately distinguishes the tool from its two nearest siblings (browser_select for dropdowns, browser_key for single keys). An agent can pick this tool without opening any schema.

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 routes two competing cases to alternatives: "Dropdowns: browser_select; single keys: browser_key." That is clear conditional guidance rather than inference. It stops short of a full when/when-not treatment (e.g. type vs. click-then-type, or whether it works on non-editable elements), so not a 5.

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