payment_guardValidate a live x402 challenge, price, Base network, USDC asset, recipient, funding, gas reserve, and destination immediately before signing.
| Name | Required | Description | Default |
|---|---|---|---|
| serviceUrl | Yes | ||
| payerAddress | Yes | ||
| expectedPayTo | No | ||
| maxAmountUsdc | Yes | ||
| minGasReserveEth | No |
Changes observed during successful MCP inspections. Dates show when Glama detected each change.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The annotations already declare readOnlyHint=true and destructiveHint=false, so no safety contradiction exists. The description adds meaningful behavioral detail beyond the annotations: the tool performs a live pre-signing validation across price, network, asset, recipient, funding, gas reserve, and destination. It could still disclose failure/return behavior, but it goes beyond a bare read-only claim.
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 a single dense sentence with no filler, and the action is front-loaded. It is concise, though the long comma-separated validation list is slightly hard to parse and some terms ('price', 'destination') remain ambiguous.
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?
With 5 parameters, 0% schema descriptions, and no output schema, the description is incomplete: it does not state what the tool returns on success/failure, whether validation failure throws or returns a reason, or how the required fields relate to the listed checks. An agent cannot fully predict invocation behavior from this definition alone.
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 0%, so the description needed to explain parameter meaning, but it never maps its listed concepts to actual parameters. The agent must guess that maxAmountUsdc is the 'price', expectedPayTo is the 'recipient', and minGasReserveEth is the 'gas reserve'; expectedPayTo and minGasReserveEth are left almost entirely to inference from their names.
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 ('Validate') and names a concrete resource ('live x402 challenge'), then enumerates the exact conditions checked (price, network, asset, recipient, funding, gas reserve, destination). This makes it distinguishable from generic sibling audit/snapshot tools, though it does not explicitly name a sibling for contrast.
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?
'Immediately before signing' gives a clear temporal context for when to invoke the tool, and 'live' clarifies it must be run against current state. However, the description does not state when not to use it or point to alternatives such as treasury_preflight or merchant_audit, so the routing guidance is implied rather than explicit.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.
Several tool pairs have heavily overlapping purposes: check_url vs verify_web_evidence vs batch_check_urls all verify public URLs, while merchant_snapshot vs merchant_audit and payment_guard vs treasury_preflight cover very similar ground. The descriptions clarify some differences, but an agent could easily select the wrong tool when names alone are ambiguous.
All names use snake_case and are readable, but there is no consistent structural pattern. Some start with verbs (check_url, verify_web_evidence), while others are noun compounds (merchant_audit, payment_guard), and batch_check_urls places the verb in the middle. The naming is understandable but not predictable across the set.
At 8 tools, the count is reasonable and within the ideal range for a focused utility server. However, a few tools are near-duplicates of others, so the set feels slightly less well-scoped than the count alone suggests.
For the apparent niche of web3 payment preflight, merchant evaluation, and URL verification, the surface covers the core workflows well. The main gap is the lack of a more granular transaction-history or payment-execution tool, but agents can likely complete their intended tasks without dead ends.