pay_and_fetch

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

With no annotations, the description carries the full burden and does so well: it warns that real money is spent, that payment is gated by per-request cap, lifetime budget, allowed hosts and chains, that these limits are operator-set and cannot be raised, and that non-paywalled resources cost nothing. This is exactly the behavioral context an agent needs before invoking a spending tool.

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 most important fact — that this spends real money — is front-loaded in the second sentence, and every remaining sentence adds a distinct constraint or edge case without repetition.

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 3-parameter, no-output-schema tool this covers purpose, cost, and gating limits thoroughly. It could say a little more about what happens on payment refusal or failure (error vs. partial fetch), which is the only remaining gap.

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%, so url, method and max_response_chars are already documented in the schema. The description adds no parameter-level meaning (e.g., unit or format of max_response_chars), so the 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?

States a specific verb (fetch) and resource, plus the distinctive behavior (automatic payment on HTTP 402). It is immediately distinguishable from siblings check_price and wallet_status, which do not fetch.

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 clear context for use: fetch a resource and pay only if it is paywalled. It does not explicitly route the agent to check_price or wallet_status first, nor state when-not to use it, so it falls short of a 5.

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