lightning_pay_invoice

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

With no annotations, the description carries the full burden. It does disclose the return payload (preimage as proof of payment, fees paid), which is valuable given there is no output schema, and 'Pay' signals a fund-moving, irreversible operation. However, it omits the critical operational facts an agent needs: the wallet must exist and be unlocked, balance must cover amount plus routing fee, and what failure modes exist (expired invoice, no route).

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 operative content is a single front-loaded sentence with zero waste. The trailing 'Tip:' sentence about earning_opportunities is off-topic for this tool and dilutes focus, costing it the top score.

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 2-parameter payment tool with no annotations and no output schema, the description covers outcome (preimage, fees) but not state preconditions or failure handling. It is adequate to identify the tool, but an agent could call it with a locked or underfunded wallet without warning.

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 100% — both bolt11 and maxFeeSats are documented in-schema, including the provider default when maxFeeSats is omitted. The description adds no format guidance or examples beyond the schema, and the phrase 'fees paid' does not clarify the maxFeeSats ceiling semantics. Baseline 3 applies.

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 names a specific verb and resource ('Pay a BOLT-11 Lightning invoice') and scopes the source of funds ('from the embedded Lightning wallet'), which cleanly separates it from lightning_create_invoice and the broader wallet/payment tools. It stops short of explicitly naming which sibling handles invoice creation, so an agent must infer the pairing.

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?

Usage is implied by the object ('a BOLT-11 invoice you already hold'), but there is no statement of prerequisites (wallet created/unlocked, funded balance) nor any exclusion or alternative routing. The one pointer offered — 'call earning_opportunities to see how to put your assets to work' — is an unrelated promotional hook, not decision guidance for this tool.

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