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

With no annotations provided, the description must carry the full burden of behavioral disclosure. It adds useful context: HMAC security for webhooks, SSE endpoint, cross-instance loop prevention via sync_peer_id, and filter requirements. However, it omits details like return value, error handling, rate limits, or what happens on success.

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?

The description is three concise sentences, front-loaded with the core action and delivery modes, followed by constraints. Every sentence adds value and there is no redundant information.

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?

Given the tool's complexity (8 parameters, no output schema, no annotations), the description covers core functionality but misses details about return values, error behavior, or how to manage the subscription (e.g., unsubscribing). It is not fully complete for an agent to invoke without additional assumptions.

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 only 13% (only sync_peer_id described), so the description compensates by explaining the role of filters (entity_types, entity_ids, event_types), delivery methods (delivery_method as 'webhook' or 'sse'), and sync_peer_id. It does not individually cover all parameters (e.g., max_failures, webhook_url) but the grouped explanation is adequate for understanding.

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 clearly states the tool's purpose: 'create a substrate event subscription (webhook with HMAC delivery, or SSE via GET /events/stream)'. It distinguishes itself from sibling tools like 'unsubscribe' and 'list_subscriptions' by focusing on creation of a subscription.

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 specifies when to use the tool by mentioning the two delivery methods (webhook or SSE) and the requirement for at least one filter among entity_types, entity_ids, or event_types. However, it does not explicitly contrast with alternatives or provide guidance on choosing between webhook and SSE, leaving some ambiguity.

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