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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered. The description adds domain context (predicted vs. realized changes) but says nothing about return shape, ordering, or whether results are capped, leaving the behavioral picture thin beyond the annotations.

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 front-loaded sentence that names the resource first and the two usage modes second. Every clause carries information and nothing is padded.

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 two-optional-parameter read-only tool with no output schema, the description covers scope and the key tonight/recent distinction. It could note that omitting names returns the full set of price-change candidates, which is the one remaining gap.

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%, so both the view enum-like values and the names filter are already documented in the schema. The description restates the tonight/recent distinction but adds no syntax or format detail beyond it, making 3 the correct baseline.

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 resource (FPL price rises and falls) and the two data modes (likely tonight vs. already made this gameweek). No sibling tool covers price changes, so the agent can distinguish it immediately.

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?

"Use this for FPL price rises and falls" gives clear usage context, and the description implies the tonight/recent split that the view parameter controls. It does not name alternatives or state when-not to use it, but no sibling overlaps enough to require that.

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