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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds real context beyond them: tier gating with a 403 plus upgrade URL, that signing secrets are always masked, and that write operations are deliberately absent from this server. That is exactly the behavioral disclosure an agent cannot get from the annotations.

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?

Front-loads the core action and the tier constraint, and every sentence carries information rather than filler. The trailing parenthetical enumerating filter fields (min_ev_pct / max_ev_pct / ev_fair_source) is dense with detail but slightly burdens an otherwise lean description.

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 compensates by naming the row fields (url, subscribed events, filters, active status) and by covering the access-tier and masking behavior. Nothing an agent needs to call this correctly or interpret the result is missing.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate and the baseline is 4. It instead spends its words on the shape of each returned row, which is useful but belongs to output rather than parameter semantics.

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 API key's webhook subscriptions') and immediately scopes it against siblings by pointing to propline_get_webhook_deliveries as the follow-up. An agent can tell this apart from the other 30+ propline tools without opening a 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?

Explicitly states when it works (Streaming Lite tier and up, others get 403 with an upgrade URL), when it will fail, and the exact ordering rule ('Use this first to find the webhook id for propline_get_webhook_deliveries'). It also rules out the alternatives for mutation by noting no create/update/delete tools exist.

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