subscribe_changes

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

No annotations are present, so the description carries the full burden. It goes beyond basic operation by disclosing the $0.20 USDC cost, x402 payment method, and the structured 402 response on payment failure or missing capability. This is valuable behavioral context, though it omits subscription management and event payload details.

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 concise, with two sentences that front-load the core action and then add cost and error handling details. Every sentence earns its place without unnecessary fluff.

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 subscription tool with no output schema, the description lacks return value info, cancellation instructions, and event payload format. It does address cost and error handling, but important operational aspects are missing, making it incomplete for a medium-complexity tool.

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 50%, with 'filter' and 'ttl_days' lacking schema descriptions. The description mentions 'matching a filter' but does not elaborate on filter fields or explain 'ttl_days', thus failing to compensate for the low coverage.

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 webhook subscription that pushes grant-change events matching a filter.' It uses a specific verb and resource, and distinctly differentiates from sibling read/search tools by introducing a subscription mechanism.

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 implies usage for receiving push notifications of grant changes, but it does not explicitly state when to use it over alternatives or when not to use it. No exclusions or comparisons to sibling tools are provided.

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