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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds genuinely new behavioral context beyond those fields: the result contents (message text with sender and thread) and the exclusion of support and assistant threads. It stays silent on result limits/pagination behavior, which keeps it short of a 5.

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, zero filler, with the resource scope and the exclusion rule front-loaded before the return-shape detail. Every clause carries information an agent needs.

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 no output schema, the description usefully states what comes back (message text with sender and thread). Annotations cover the safety profile. The only gap is that conversation_id is defined nowhere, which is a minor incompleteness for a 4-parameter search tool.

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 coverage is 75%, and the three documented parameters (days, limit, query) are already explained in the schema. The description restates keyword and date filtering but adds no syntax, defaults, or format detail, and conversation_id remains undocumented in both places. Baseline 3 for high schema coverage 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 (Searches) and resource (this user's Widely, SMS, and WhatsApp threads) with the matching dimensions (keyword and date), and gives the return shape (message text with sender and thread). It also names what is out of scope (support and assistant threads), which separates it from read_support and search_calls without opening their schemas.

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 note that support/assistant threads are excluded, which hints at when this tool is and isn't the right one. However, no alternative is named and no prerequisite or context for choosing it over get_thread or read_support is given, so the guidance stays inferential rather than explicit.

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