Read Messages

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

Annotations already declare readOnly/idempotent/non-destructive, so the 'read-only with no side effects' sentence is largely redundant, but it does not contradict them. The description adds real behavioral value beyond annotations: messages come back newest-first, and each item carries sender, date, body, reactions and attachment metadata. It omits pagination/limit behavior, which keeps it from 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?

Four short sentences, front-loaded with what the tool returns and in what order, then contents, safety, prerequisite, and alternative. No filler.

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?

Output schema exists, schema coverage is complete, and annotations cover the safety profile, so the description only needs orientation — which it provides (ordering, contents, prerequisite, alternative). Slight gap: no mention that results are paginated via limit/offset, though the schema covers it.

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 after/before/limit/offset/chat_name are already fully documented in the schema. The description only reinforces the case-sensitivity prerequisite for chat_name and adds nothing about the time-window or pagination parameters, 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 and resource (read messages from a single Signal chat) plus an important scope detail: returned newest-first. It explicitly distinguishes itself from both list_chats (name source) and search_messages (keyword search across chats), so an agent can pick it without reading 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?

Gives a prerequisite (exact chat name from list_chats) and a named alternative with the condition that selects it ('Use search_messages instead to find messages by keyword across chats'). Both when-to-use and when-not-to-use are covered.

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