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

readOnlyHint=true already tells the agent this is a safe read, so the bar is lower. The description adds genuine value by disclosing what the response contains (URL, event types, channels) and the underlying REST route, which matters because there is no output schema. It stops short of noting failure modes (e.g. unknown endpoint id) or auth requirements.

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, front-loaded with the payload summary and followed by the REST mapping; no filler. The GET path is slightly redundant for an agent that only needs the tool contract, but it is compact and useful for API-literate callers.

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-required-param read with full schema coverage and a readOnly annotation, the definition covers purpose, return contents and endpoint binding. The only missing piece is error/empty behavior, which is minor given the tool's simplicity and lack of an output schema.

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 both app_id and endpoint_id are fully documented in the schema, including the ep_... id format. The description adds nothing about parameters 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?

States a specific verb and resource ('Fetch a single webhook endpoint') and enumerates the data it exposes (URL, subscribed event types, channels). The word 'single' plus the field listing cleanly separates it from svix_list_endpoints and svix_get_endpoint_stats 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?

Use is only implied: 'a single' suggests one record vs the list sibling, but there is no explicit when-to-use statement, no prerequisites (e.g. needing a valid ep_ id), and no named alternative. Adequate but leaves the selection reasoning to inference.

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