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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the explicit "Read-only." repeats structured data. However, the description adds genuinely new context: what the output is for, and a caveat that the tool is rarely needed and the user should not be prompted to choose. That goes meaningfully beyond the annotation set.

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, front-loaded with purpose, then usage, then the caution. Every sentence carries weight except "Read-only.", which duplicates the readOnlyHint annotation and could be dropped. Very near optimal otherwise.

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?

An output schema exists, so return values need not be re-explained; the description still usefully says what the IDs are for. Combined with the when-to-use guidance and the no-parameter schema, an agent has everything needed to call this correctly.

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?

The tool takes zero parameters and schema coverage is 100%, so there is nothing for the description to disambiguate. The baseline for a parameterless tool applies; no additional meaning is required or missing.

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 ("List available browser environments (persistent profiles)") and clarifies the payload's purpose by noting it returns environment IDs. It also names the sibling tools that consume those IDs (browser_task, create_session), letting an agent place it precisely in the tool graph.

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 when the tool is needed (persistent sessions in browser_task or create_session) and when it is not (workflows and agents use the connection's environment automatically). It even gives a behavioral instruction — do not ask the user to choose an environment — which is exactly the routing guidance an agent needs.

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