Thread

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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds a genuinely useful behavioral constraint beyond that: it returns only the author's own continuation, not all replies, which prevents a common misinterpretation of what 'thread' means here.

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 sentence with zero filler, front-loading the verb and resource and then qualifying the scope. Nothing could be removed without losing meaning.

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 three fully documented parameters, no output schema, and annotations covering safety, the description supplies enough to call it correctly. A note on result size or whether the chain is truncated would close the 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% — the schema documents ref, the compact/full format enum, and the days_forward range. The description adds no parameter-level detail such as accepted ref forms or the 14-day forward limit, so baseline 3 applies.

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 verb ('Reconstruct') and resource ('the thread around a tweet') and defines the exact scope: ancestors above plus the author's own continuation below. That scope implicitly separates it from generic fetchers like ca_get_tweets or ca_search_tweets, though no sibling is named outright.

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?

Usage is implied by the scope description rather than stated: an agent can infer it is the tool for thread reconstruction, but the description gives no explicit conditions, prerequisites, or when-not guidance against alternatives like ca_get_tweets.

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