Get one message

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 one genuinely useful constraint — the chat must be allowlisted — but says nothing about what happens when the id or chat is not allowlisted, nor about error/no-result behavior.

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 front-loaded sentence with no filler; the resource, the lookup key, and the access constraint are all stated up front.

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 simple two-parameter read with full schema coverage and no output schema, the definition is minimally sufficient — an agent knows what to call and how. It stops short of describing failure modes (non-allowlisted chat, unknown message id) that would matter for a tool restricted to an allowlist.

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%, and both parameters (chat formats, messageId bounds) are already documented in the schema. The description adds no format or semantics beyond that, so the 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?

The description names a specific verb and resource ("Fetch a single message by id") and narrows scope to "an allowlisted chat." The word "single" implicitly separates it from the bulk sibling get_messages, though no sibling is named explicitly.

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 only implied: retrieving one message by id vs listing via get_messages or querying via search_messages. There is no explicit when-to-use/when-not clause and no statement of prerequisites beyond the passing mention of the allowlist.

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