First said

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

Annotations already provide readOnlyHint=true and openWorldHint=true, so safety and world-access behavior are covered. The description adds that results come from an archive and can be scoped overall or to one person, but it does not disclose that the 'scan' limit may bound how far back the earliest result can be found.

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 tight sentences with no filler, front-loading the core operation before giving concrete example questions. Every sentence contributes to understanding the tool.

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 seven-parameter read-only tool with no output schema, the description covers the central intent and person-scoping behavior. However, it does not explain the roles of optional parameters like n and reply_to_user, nor does it warn that scan limits may affect the search completeness.

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?

With 57% schema description coverage, the schema already documents q, scan, since, and until. The description clarifies the word/phrase matching and the 'one person' scope, but leaves n, reply_to_user, and the scan-limit implications largely undocumented beyond the schema.

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 states a specific verb and resource: 'Find the earliest archived tweets containing a word or phrase.' It also adds scope ('overall or by one person') and a clear first-said use case, though it does not explicitly name sibling alternatives such as ca_search_tweets or ca_phrase_timeline.

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 gives clear usage context through the questions 'when did I first say X' and 'who said it first,' which tells the agent when this tool is appropriate. It does not state exclusions or name alternative tools, so it falls short of the top score.

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