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

With no annotations, the description fully discloses behavioral traits: paid subscription ($0.01), 30-day window, eventual drift events, one-time firing semantics, required x402 payment, and response type ('Returns payment instructions'). It also reveals side effects like receiving extra events unless configured, and identifies event headers/schema.

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 long but information-dense, covering purpose, events, payment, and configuration in a few sentences. It's front-loaded with the core action, and each clause adds relevant detail. However, the single-block paragraph could be more scannable with bullet points, slight structural deduction.

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 complex 7-parameter tool with no output schema, the description covers behavior well but under-specifies the return value ('Returns payment instructions' is vague). It doesn't mention whether a subscription ID is returned (needed for unsubscribe/list), nor error/edge cases like callback verification. The webhook event schema is named but not detailed. More would be expected given no output schema.

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 baseline is 3. The description adds value by explaining the functional relationship between threshold_score and drift muting ('Set 100 to mute drift events'), and the warning-window behavior of attestation_expiry_warning_days, which goes beyond the schema's simple property descriptions.

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 uses a specific verb ('Subscribes') and resource ('webhook URL to receive signed POST alerts'), and clearly states the two event triggers (attestation.expiring_soon, attestation.expired). It also distinguishes itself from sibling 'subscribe_reputation_drift_alerts' by explaining how drift events are included and how to mute them.

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 when to use this tool by explaining the subscription mechanism and payment requirements, and it explicitly contrasts with reputation drift subscriptions ('threshold_tier_change=false... Set 100 to mute drift events'). It lacks a direct 'use this instead of X' statement but provides enough context to choose correctly.

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