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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds ordering ('newest first') and the REST mapping, but says nothing about pagination behavior, default result caps, or auth requirements beyond what the schema already carries.

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 tight sentences: purpose and ordering first, filters second, REST endpoint last. Zero filler and nothing redundant.

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 read-only list tool with 100% schema coverage and no output schema, the description covers purpose, ordering, and filter surface adequately. It stops short of explaining the iterator-based pagination flow, which a calling agent would benefit from given the 'limit' and 'iterator' parameters.

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 100%, so each of the 9 parameters is already documented in the input schema. The description only restates the filter categories in prose, adding no syntax or format detail beyond what the schema provides — 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?

States a specific verb and resource ('List the webhook messages'), scopes it to one application, and specifies ordering ('newest first'). It largely distinguishes itself from siblings like svix_get_message and svix_list_attempts_by_message, though it never names an alternative 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?

The description enumerates the filter dimensions (event type, channel, tag, time window), which implies how to narrow results, but gives no when-to-use guidance, no prerequisites, and no exclusions versus sibling list tools such as svix_list_endpoint_messages.

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