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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds genuinely useful behavior beyond that: the relative cost and fidelity of each mode ('cheapest, structure only', 'roughly 40 characters per pixel'), and the explicit limitation that it cannot convey subtle typography or design intent. No return-format or pagination detail is given, keeping it from a 5.

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?

Purpose is front-loaded in one line, followed by a compact per-parameter block and a closing limitation. The mode tests ('layout, colour and shape' / 'structure only') are terse and each sentence carries information, though the run-on mode paragraph is slightly dense.

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?

There is no output schema, so the description is right to characterize output fidelity and limits. For a 6-parameter renderer it covers the parameters that matter most and explains the output's nature, with only 'colors' and 'device' left unexplained.

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 0%, so the description must carry the load, and it does for four of six parameters: mode (all three values explained), crop (all named values plus the 'a,b' fraction format), cols (output width), and squash (scale factor with default 1.0 semantics). 'colors' and 'device' are never mentioned, leaving a gap that prevents a 5.

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?

Opens with a specific verb+resource: 'Render the current screen as text.' It immediately distinguishes itself from the sibling screen_tree by stating its output is a rendered approximation rather than exact content. An agent can identify the tool's role without opening the 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?

Names screen_tree as the alternative and states the condition that selects it ('exact content'), and warns that this tool does not convey small body text or design-intent matching. It also gives the mode-specific guidance to keep 'ansi' to small crops. No explicit when-not for the other siblings (tap, audit_layout), so not a full 5.

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