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

With no annotations, the description carries the disclosure burden. It does this well: it states it 'only lists past/current registrations,' clarifies that it cannot hold open an SSE stream, and points to the raw HTTP endpoint for registration. It falls just short of describing the returned payload shape or pagination, but it provides strong behavioral context beyond simple verb-resource semantics.

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 dense sentences with no filler. The core purpose is front-loaded, followed immediately by sibling distinction and a critical behavioral limitation. Every clause earns its place.

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 low-complexity read-only listing tool with one optional parameter, the description is complete: it covers what is listed, who it is scoped to, how it differs from the sibling, and why registration is out of scope. The absence of a return-type specification is acceptable for a list operation whose nature is clear from the description.

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%, and the schema already fully describes owner_key including the default behavior from the Authorization header. The description's 'for your account' reinforces the parameter's scope but does not add meaningful detail beyond what the schema provides, 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 states a specific verb and resource: 'List SSE_hook registrations for your account.' It clearly distinguishes this tool from the sibling list_webhook_targets by describing it as the 'long-lived-outbound-stream sibling' and by specifying the subscriber context ('no stable inbound address').

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 explicitly names the alternative list_webhook_targets and gives the selection condition ('for subscribers with no stable inbound address'). It also states that registration happens over the raw HTTP POST /sse-hooks endpoint and that this MCP call cannot hold the SSE stream open, effectively telling the agent when not to use this tool.

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