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

Annotations already declare readOnlyHint=true, openWorldHint=true, idempotentHint=true, and destructiveHint=false. The description adds value by specifying cursor-paginated behavior and clarifying the return type (user objects, not tweets). It also differentiates retweets from quotes, which is behavioral context not in the annotations. It doesn't cover rate limits or auth, but given the read-only nature and rich annotations, a 4 is appropriate.

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?

Two sentences with no filler. The primary action and key distinction are front-loaded, and the alternative tool is mentioned concisely. Every word earns its place.

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 simple read-only list tool with an output schema, rich annotations, and a clear description that covers purpose, usage, and sibling differentiation, nothing critical is missing. The agent can call this correctly without further clarification.

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%: both tweetId and cursor have descriptions. The description mentions cursor-paginated but does not add syntax or format details beyond the schema. Since the schema already documents both parameters adequately, the baseline of 3 is correct—the description adds marginal semantic value.

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 starts with a specific verb and resource: 'List the accounts that retweeted a given tweet.' It clearly states the output (user objects) and explicitly distinguishes from a sibling tool (get_twitter_tweet_quotes) by saying it returns retweeters, not quoted tweets. This makes the purpose unambiguous.

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?

It provides a clear when-to-use context: 'Use this to map who amplified a message and how influential they are.' It also gives an explicit alternative for a different use case: 'For retweets that added commentary use get_twitter_tweet_quotes.' This tells the agent exactly when to choose this tool over a closely related one.

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