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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds useful context by specifying the computation source (agents.weekly_delta) and the default limit of 10 per direction, which goes beyond the annotation metadata without contradicting it.

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 two concise sentences, front-loaded with 'Returns' and no filler. It efficiently communicates the core functionality and the default behavior.

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?

With all parameters optional and well-documented, an output schema present, and annotations covering safety, the description provides sufficient context for a read-only query tool. It clearly answers what, when, and basic behavior without needing to explain return values thanks to the output schema.

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% for all three parameters, each with its own description and defaults. The description does not add parameter-specific information beyond the schema, so the baseline score of 3 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 clearly states the tool returns top weekly rank movers computed from agents.weekly_delta, with up and down directions. It uses a specific verb ('Returns') and resource ('top weekly rank movers'), which makes it distinguishable, although it does not explicitly name sibling alternatives.

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?

The phrase 'Useful for surfacing notable changes since last week' provides clear context on when to use the tool. It does not enumerate when not to use it or mention alternative tools, so it misses the top tier, but the context is still informative.

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