list_chats

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

Annotations already declare readOnlyHint, idempotentHint, non-destructive, and closed-world, so 'Read-only with no side effects' is largely redundant. However, the description adds behavior the annotations do not: the sort order (most recent message) and the local-database scope, which help predict results.

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?

Purpose and sort order are front-loaded, followed by result fields and routing guidance; every sentence contributes. The 'Read-only with no side effects' clause is redundant with the annotations and is the one phrase that does not earn 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?

With rich annotations, a 100%-covered input schema, and an output schema handling return values, the description covers everything an agent needs: what is returned, ordering, safety, and which sibling to prefer. No material gap remains.

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%, so limit and query are already fully documented with defaults and ranges. The description adds no parameter-level detail (e.g., filtering semantics or pagination interaction) beyond what the schema provides, so the baseline of 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 and resource ('List direct and group Signal chats'), names the data source ('local desktop database'), and the ordering ('sorted by most recent message'). It also distinguishes itself from the list_groups sibling, so an agent can select it without opening any schema.

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?

Explicitly names the downstream use case ('discover exact chat names before calling read_messages or search_messages') and the exclusion ('Use list_groups instead when you need group_id values for send_message'). Both when-to-use and the alternative tool are spelled out.

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