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

Annotations already cover safety (readOnlyHint true, destructiveHint false, openWorldHint false). The description adds meaningful behavioral context beyond that: it specifies the web-only scope, the error behavior for app sessions, and that it returns per-step screenshot URLs. It does not cover pagination or auth requirements, but for a read-only tool this is a strong addition.

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 tight sentences with zero waste: the core action and return value are front-loaded, followed by scope constraints and the alternative tool. Every sentence earns its place.

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 no output schema, the description still tells the agent what to expect (screenshot URLs for each step). It also fully covers the key usage boundary (web vs app automation) and points to the sibling that handles app sessions, so an agent has all needed context 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?

Schema description coverage is 100% for the single sessionId parameter, which already documents its expected format (e.g., DA-WIN-...) and dual meaning (test ID or session ID). The description adds no further parameter detail, 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 (retrieve) and resource (command-by-command screenshots captured during a test session), and immediately clarifies the output (screenshot URLs for each step). It also distinguishes itself from sibling getSessionVideo by focusing on screenshots and from listMobileSessions by confining scope to web automation.

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 to use this tool (web automation sessions only) and when not to use it (app automation sessions return not found). It names the alternative tool for app sessions (listMobileSessions), leaving no ambiguity about routing.

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