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

Annotations already cover the safety profile (readOnlyHint, idempotent, closed-world), but the description adds genuine context beyond them: the screen is fixed, thresholds and sector exclusions are not adjustable, and results match a published page. It also disclaims interpretation ('screen output, not recommendations, and neither label forecasts a return'), which helps an agent relay results responsibly.

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?

Front-loaded with the core action, then definitions, then routing, then caveats — a sensible order with no repetition. Slightly longer than needed; the final caveat sentence could be tighter, but each sentence carries distinct information.

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?

No output schema exists, so the description carries the burden of explaining results, and it does name and characterize both returned lists. It stops short of describing the record shape (fields per company, ordering, count), which is the remaining gap for a parameterless list tool.

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?

Zero parameters gives a baseline of 4, and the description justifies the empty schema rather than ignoring it ('Takes no parameters: the thresholds, sector exclusions and ranking are fixed'), pre-empting an agent's attempt to pass filter arguments.

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 ('Returns the two lists Zyberno publishes each month from one fixed screen') and then defines the contents of both lists by name and criteria. An agent can distinguish this from screen_stocks or get_stock_valuation purely from the description.

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 enumerates the triggering user intents ('what the framework currently flags', asking for the Double Discount or value trap lists by name) and explicitly names the exclusion cases with the correct alternative for each (screen_stocks for custom criteria, get_stock_valuation for a single company). Nothing is left to inference.

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