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

The readOnlyHint annotation already establishes this as a safe read. The description adds that the response includes the event type and payload, and the schema notes with_content defaults to true, but it does not cover error behavior for a missing msg_id or any auth/lookup-failure context.

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 waste, with the substance front-loaded ahead of the REST path reference. Nothing to trim.

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 signals the return contents (event type and payload), which is what an agent needs to decide between full and content-less retrieval. Permissions and not-found behavior are unaddressed but are minor for a read-only fetch.

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 all three parameters (including the with_content default) are already documented. The description adds no syntax or format detail beyond the schema; the mention of 'payload' only loosely maps to with_content. Baseline 3 is appropriate.

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 ('Fetch a single message') and names what comes back (event type and payload), which separates it from list-style siblings. It does not explicitly name svix_list_messages as the alternative, but 'a single message' is clear enough to route correctly.

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 required app_id/msg_id pair and the REST path, so an agent can infer this is the by-id retrieval tool. There is no explicit when-to-use vs. svix_list_messages or svix_list_attempts_by_message guidance, and no stated prerequisites.

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