Focxle: virtual cards, spend limits and procurement for AI agents

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

With no annotations, the description carries the full burden and it is unusually candid: one-call/no-signup behavior, no money custody, no storage of card/account numbers, and a portable identity that follows the agent because it self-reports. It also reveals the owner-approval follow-up, which materially affects what the caller should do after the call.

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 purpose is front-loaded and every block adds some information, but the prose is promotional and wordy ('in ONE call with no signup, no email and no account', the long 'follows YOU' sentence). It could be tightened to two or three factual sentences without losing value.

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 zero-required-parameter registration tool with no output schema, it tells an agent why to call it, what happens as a result, and the necessary follow-up (send the returned link to the owner). It leaves minor gaps around the exact response shape, but it is otherwise complete.

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 the baseline of 3 applies. The description adds no detail about name, purpose, or services beyond what the schema already documents.

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 opening verb 'Register' plus 'this agent for spending' identifies a specific action and target resource, and the rest clarifies it creates an agent identity and payment record. This clearly separates it from budget, card, and deal tools even without naming a sibling.

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?

It conveys a clear context—register once before spending so suppliers can read the agent's payment record—and it tells the caller to send the owner the resulting link. However, it never says when not to use it or names alternatives such as budget_request_increase or payments_how_it_works, so the use-vs-alternative guidance is only implied.

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

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

With no annotations at all, the description carries the full burden and does exceptionally well: it discloses card creation timing, hard amount cap, merchant lock, single-use behavior, issuer relationship, no retention of card numbers, registration side effect, and the budget-link fallback.

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 key purpose is front-loaded and the structure is logical (purpose → examples → behavior → trust → onboarding). It is longer than strictly necessary, with some redundancy like 'single-use' and 'cannot be spent twice', but every section adds relevant operational context.

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 no-annotation, no-output-schema tool with nested parameters, the description is complete about side effects, registration, budget handling, and trust boundaries. It does not describe the returned card payload, but the rest of the context is strong enough to make the tool callable.

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 already 75%, so the baseline is 3. The description adds meaningful context beyond the schema by tying 'payee' to the merchant lock and 'amount' to the hard cap, and by noting the reason is recorded but never used for the decision.

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 opening sentence names a specific verb ('Get'), a specific resource ('single-use virtual card'), and an immediate purpose ('buy something right now'). The following examples make the scope unmistakable and implicitly distinguish it from sibling approval/history/record tools.

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?

It gives a clear 'when to use' with an extensive list of procurement scenarios (SaaS, domains, hosting, checkout). It does not explicitly say when not to use it or name an alternative, so it stops 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.

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

No annotations are provided, so the description carries the full burden. The verb 'Read' strongly implies a non-destructive operation, but the description does not explicitly state it is read-only or mention any side effects, auth requirements, or rate limits. It also doesn't clarify whether the 'next steps' are suggestions only. This is adequate but not exhaustive.

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 two sentences with no fluff. The first sentence front-loads the core purpose, and the second expands on the output details. Every phrase contributes to understanding the tool, making it highly efficient.

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 zero-parameter tool with no output schema, the description is remarkably complete. It covers what the tool does, what data it reveals, and even a use case (sharing the link). Nothing essential for an agent to decide to call it is missing.

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?

With zero parameters, the schema is empty and the baseline is 4. The description adds value by explaining the tool's output and purpose, compensating for the lack of any parameter information. It clearly describes what the user will see, which is more than a generic placeholder.

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 reads your own payment record and score, with a specific verb and resource. It goes beyond a simple definition by listing what it shows (logged entries, confirmations, ceiling, shareable link), distinguishing it from generic payment tools. Though it doesn't name a sibling, the scope ('your own') and purpose ('raise it') are unambiguous.

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 it: when you want to view your personal payment record and get actionable advice. It doesn't explicitly contrast with siblings like payment_record or payments_how_it_works, but the self-referential language ('your own', 'share with anyone deciding whether to deal with you') gives clear context. No exclusions are stated, but the use case is evident.

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

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

With no annotations, the description carries the full burden of behavioral disclosure, and it does well: it reveals that account numbers, card numbers, and keys are stripped before persistence, that each payment affects the user's score, and that a confirmation link is returned for the payee. It does not mention rate limits or authorization, but the data-handling and scoring side effects are clearly stated.

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 front-loaded with the core purpose and then uses each subsequent sentence to add a distinct piece of behavioral context: platform flexibility, score impact, confirmation workflow, and data scrubbing. It is slightly wordy in the 'any procurement system nobody has heard of' phrase, but no sentence is wasted.

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?

The tool has 8 parameters, nested objects, no output schema, and no annotations, yet the description supplies enough operational context to call it correctly: what counts as a valid submission, how platform is handled, the confirmation flow, and privacy safeguards. It only partially describes the return value (one-click link, ceiling rise), but the essential invocation context is present.

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 75%, so the baseline is 3. The description reinforces the purposeful use of platform and external references ('any payment provider', 'you tell us') and warns against sensitive identifiers, but it does not add substantial parameter-level semantics beyond the schema's own 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 opens with a specific verb and resource: 'Submit a receipt or invoice for a payment you already made' and clarifies the cross-platform scope. This clearly distinguishes it from siblings like payment_history_mine (reading history), spend_request_approval (approving before spending), and card_get_virtual (issuing cards).

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 gives a clear trigger: use this for payments already made on any platform, regardless of integration. It does not explicitly name sibling alternatives or give 'when not to use' exclusions, so it stops short of a 5, but the context is unambiguous for an agent choosing among the listed siblings.

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

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

With no annotations, the description carries the full burden. It discloses the tool returns only an eligibility decision (no payment side effect) and describes the watch-only mode behavior ('we always allow and tell you what would have been stopped'). This goes beyond a generic 'check' and signals it is non-destructive. It doesn't explicitly state auth requirements or that it never executes a payment, but the contrast with card_get_virtual and the 'safe to call' wording make this clear enough.

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 front-loaded with the core purpose and then adds usage guidance and edge-case behavior. It is slightly wordy (the first two sentences are similar), but every sentence contributes meaning: scope, output, when to use, alternative, and watch-only safety. No filler, though it could be tightened slightly.

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?

Given no output schema, the description compensates by stating the return shape ('allowed or not, and which limit or rule stopped it'). It covers the key use case, prerequisites (watch-only mode adds a safety net), and differentiates from the payment card tool. It does not describe how to construct the nested payee/amount objects or the exact response format, but the schema and the high-level output hint are sufficient for correct invocation in most agent workflows.

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 60%, with some parameters (payee.ref, intent, idempotency_key) already described. The description adds context that amount and payee are used to assess limits/rules, and that replies are idempotent for the same payment. However, it doesn't elaborate on structure for nested objects (e.g., how payee.name/category or amount.value/currency are interpreted) or on the format of the idempotency key beyond what the schema says. This is adequate but not a strong supplement to the schema.

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 opens with a clear verb and resource ('Check your budget before you buy') and then specifies exactly what it checks: 'daily spend limit and the procurement rules your owner set.' It states the output ('allowed or not, and which limit or rule stopped it') and differentiates from card_get_virtual, a key sibling. An agent can tell this is an eligibility check, not a payment tool.

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?

Explicitly states when to use: 'Use this when you already have a way to pay and only need to know if you are allowed.' It names the alternative, card_get_virtual, for when a card is needed. It also covers a special case (watch-only mode) and explicitly says it's safe to call before checking is enabled, leaving no ambiguity about prerequisites.

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

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

No annotations are provided, so the description carries the full burden. It discloses the flow (returns a link and words to send), the owner's process (writing rules in plain English), and security reassurances (no password or bank details). However, it does not mention potential failures (e.g., approval being denied) or side effects beyond the request creation, so it is thorough but not exhaustive.

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 paragraph that is front-loaded with the core purpose and then explains the process. It is efficient, with no redundancy, and every sentence contributes to understanding the tool's functionality and safety. It is slightly longer than necessary but remains readable and well-structured.

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?

The description explains the return value (a link and words), the owner's interaction, and the ongoing enforcement of rules. It covers the essential aspects for an agent to invoke the tool correctly. However, it does not address edge cases like what happens if the owner rejects the request or how to interpret the response, which would be useful but not critical given the tool's simplicity.

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?

The input schema has zero parameters, so the description does not need to explain parameter semantics. The baseline for 0 params is 4, and the description adds context about what the tool achieves without needing parameter details. It appropriately focuses on behavior rather than parameters.

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 states a specific verb ('Ask your owner') and resource ('bigger budget' or 'permission to buy something they have not allowed yet'). It clearly distinguishes itself from sibling tools like budget_request_increase by covering both budget increases and approval for unallowed purchases, and it describes the expected outcome (link and words to send). The purpose is unambiguous and actionable.

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 clearly indicates when to use the tool (when you need budget or permission for an unallowed purchase), but it does not mention any alternatives or explicitly state when not to use it. While the context is clear, it lacks exclusions or comparisons to sibling tools like budget_request_increase, leaving some ambiguity about edge cases.

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

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It clearly explains the return payload (payment record details and a 0–1000 score), and crucially discloses a behavioral limitation: records not confirmed by others are capped at 450 and the tool explicitly states this to avoid false confidence. It also mentions being free and requiring no account. While it does not explicitly state it is read-only, that is implied by the nature of a check. Missing explicit mention of data freshness or potential errors, but the disclosed cap and scoring logic add significant behavioral context.

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 moderately long but every sentence carries value: purpose, return contents, the scoring limitation, the free/no-account note, and the sibling alternative. It is front-loaded with the core purpose and maintains focus. While not the shortest possible, it is appropriately structured and free of filler.

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?

Given that this is a read-oriented check with no output schema, the description covers everything an agent needs to call it correctly: the purpose, the data returned, the scoring behavior, the cap on unconfirmed data, the cost/friction (free, no account), and the alternative for a different input type. No critical operational detail is missing.

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?

The schema has 100% description coverage for both parameters (agent_id and limit), so the description does not need to elaborate. The description adds no additional meaning about the parameters themselves—it does not mention how limit affects results or any format specifics. Per the rubric, with high schema coverage the baseline is 3, and the description does not exceed it.

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 identifies the tool's purpose with a specific verb ('Check whether'), a precise resource ('an AI agent'), and the decision contexts ('before you sell to it, extend terms to it, or take work from it'). It explicitly distinguishes itself from the sibling trust_check_wallet by stating the alternative for crypto wallets. This fully disambiguates it from nearby tools.

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 states explicit usage contexts (before selling, extending terms, or taking work) and provides an alternative ('For a crypto wallet rather than a registered agent, use trust_check_wallet instead'). It also includes operational guidance: 'Free, no account.' This leaves no ambiguity about when to invoke this tool versus its sibling.

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