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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds behavioral context beyond this: it reveals the tool compares historical snapshots, outputs three categories of change, and depends on prior snapshot accumulation. No contradiction exists.

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?

The description is a single, compact sentence that front-loads the core function and immediately follows with the prerequisite. Every word adds value; there is no redundancy or filler.

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 read-only analysis tool with one optional parameter and rich annotations, this description is complete: it states what the tool does, what inputs are needed (implicitly the platform param), and the precondition. No output schema is present, but the output categories are clearly enumerated, so the agent can anticipate the return shape.

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?

Only one parameter exists (platforms) and the schema description covers it fully ('可选，限定平台，逗号分隔；默认核心平台'). The tool description adds no additional meaning about this parameter, so the baseline of 3 for 100% schema coverage is appropriate.

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?

The description explicitly states the tool compares historical snapshots and outputs newly listed, ranked-up (≥3 positions), and dropped-off topics per platform. The verb '对比' (compare) plus specific output categories clearly distinguishes it from siblings like get_trending (current list) and take_snapshot (capture a snapshot).

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?

Provides an explicit precondition: at least two snapshots are required, and it names the alternative paths to obtain them ('get_trending 会自动积累，或用 take_snapshot'). This directly tells an agent when to use this tool and which sibling tools to call first if the condition isn't met.

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