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

Annotations supply only destructiveHint=true, so the description carries the burden and does so well: it discloses that the call may return an already-existing recipient (idempotent dedupe), that the new recipient is auto-attached to ALL existing checks unless selected=false, that an API key is required, and that some integrations require prior web-UI setup. These are exactly the side effects an agent needs before mutating alert routing.

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?

Information-dense and front-loaded: purpose and return value come first, then side effects, then prerequisites. The middle clause stacking several URL types is slightly run-on, but no sentence is filler.

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 steps in by describing the return ('the new (or already-existing) recipient with its id'). Combined with the prerequisite and default-selection notes, an agent has enough to call it correctly; only error/failure modes (invalid webhook, duplicates by value) are unaddressed.

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 the baseline is 3, but the description adds meaning by mapping each type to the corresponding value format ('phone number (sms)', 'Slack-compatible incoming-webhook URL', 'Microsoft Teams webhook URL'), which the schema's plain enum does not explain. It also restates the selected=true default in behavioral terms.

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+resource ('Add an alert recipient') and immediately enumerates the accepted recipient forms, so an agent can tell it apart from updown_list_recipients without opening the schema. The endpoint hint ('updown: POST /api/recipients') reinforces exactly what object is created.

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?

Gives real preconditions: read/write API key required, and Slack/Telegram/Zapier/Statuspage integrations must already exist in the web UI. It also explains the default selection behavior and how to opt out with selected=false. It stops short of naming the sibling tool for listing existing recipients, so it is clear context rather than full when/when-not routing.

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