Look at the screen

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

readOnlyHint=true already declares the safety profile, and the description adds genuinely new information: the return content is a numbered element list plus a screenshot, with the conditional that screenshot=false suppresses it. No output schema exists, so this disclosure of return shape is doing real work.

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?

A single sentence, front-loaded with the core action, with zero filler. Every clause carries information: the read verb, the two return components, and the one condition that changes output.

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 zero-required-parameter read-only inspection tool with full schema coverage and no output schema, this covers what to call and roughly what comes back. It could go further by explaining that the numbered element list is what other tools (e.g. phone_tap) address by index, which is the key downstream use.

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 both parameters are already documented in the schema. The description echoes the screenshot toggle's conditional behavior but adds no syntax or format detail beyond it, and says nothing about the serial parameter. 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 ('Read the current screen') and specifies exactly what comes back: the numbered element list plus a screenshot. It's clearly distinct from siblings like phone_tap or phone_shell by being an observation tool, though it never names those siblings explicitly.

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?

Usage is only implied: as a 'read the screen' tool an agent can infer it's the inspection step before acting. There is no explicit when-to-use statement, no mention of calling it before phone_tap/phone_type, and no alternatives discussed.

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