HTTP 402 AI Tollbooth

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is established. The description adds value by specifying the exact artifacts it will not create (invoice, checkout, payment), which is concrete context beyond the generic hints. No contradiction between description and annotations.

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?

Two sentences totalling 13 words, with the core purpose front-loaded in the first sentence. Every word earns its place; the second sentence is a precise exclusion rather than 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?

For a one-parameter read-only tool the core is covered, but with no output schema the phrase 'purchase directions' leaves the return format undisclosed (plain text steps, structured list, URL?). The expected format of the `product` parameter is likewise absent. Adequate but with clear gaps.

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%, and the description never mentions the sole required parameter `product`. The agent cannot tell whether to pass a product name, ID, or slug; maxLength/minLength provide no semantic help. The description fails to compensate for the coverage gap.

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 and resource ('Return purchase directions only') with a boundary condition that disambiguates from the name's implication of an actual transaction ('Never creates an invoice, checkout, or payment'). The scope is unambiguous on its own, though it does not explicitly contrast with sibling 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 usage context is implied — this tool is for when a user needs purchase directions — but no explicit when-to-use versus alternatives guidance is given. The negative guarantee ('Never creates an invoice, checkout, or payment') signals it is not for executing purchases, but no sibling is named as the alternative for that need.

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?

Annotations already cover the safety profile: readOnlyHint, idempotentHint, and destructiveHint are all provided. The description adds 'public' and 'availability', which usefully imply no authentication and possibly dynamic state, but it does not disclose return behavior or any operational characteristics beyond what annotations already establish. No contradiction exists.

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, front-loaded sentence with no filler. Every word adds meaning: 'Read' signals the operation, 'public' signals access scope, and 'payment-method availability' signals the resource.

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, read-only tool with rich annotations, the description is largely complete. The main gap is that there is no output schema and the description doesn't specify the return shape, but the tool name and 'availability' strongly imply a list of payment methods with availability status.

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 tool has zero parameters and the schema coverage is 100%, so the schema leaves nothing undocumented. The description doesn't need to explain parameter meaning; the baseline for a zero-parameter tool is met.

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 clear action ('Read') and a specific resource ('public payment-method availability'), which distinguishes it from siblings like buy_product, list_products, and preview_product. The resource is concrete enough for an agent to understand what the tool does without opening the schema.

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 no guidance on when to use this tool versus the sibling tools. It doesn't mention that this should be checked before buy_product, nor does it rule out list_products or preview_product as alternatives. The agent must infer usage from the tool name alone.

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?

Annotations already cover the safety profile with readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the bar is lower. The description adds genuinely useful behavior beyond those annotations: the result set is capped at 50 products and the search is scoped to the public catalog. It does not describe pagination or ordering, but for a simple read-only search this is a minor gap.

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?

A single sentence that front-loads the verb, names the resource, and folds the key constraint inline. Every word earns its place; nothing is redundant and the structure is optimal for agent scanning.

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 simple read-only tool with three optional scalar parameters and no output schema, the description covers the core facts an agent needs: purpose, scope (public catalog), and the 50-result cap. The main gaps are that the return format is unspecified (no output schema exists) and behavior with no arguments is implicit, but these are minor given the tool's low complexity.

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 0% schema description coverage, the description carries the burden of explaining the three parameters, but it only implicitly touches them: 'search' hints at query's role and 'maximum 50' maps to the limit cap. The category parameter is entirely undocumented in the description, and how the parameters combine (AND vs OR, precedence) is left to inference.

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 the specific verb 'search' and identifies the resource as the 'public catalog' of products, making the tool's function unmistakable. The 'public' qualifier and search framing clearly distinguish this from the sibling tools buy_product, preview_product, and list_payment_methods.

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 this is the discovery surface for the public catalog, but it never explicitly states when to prefer this over preview_product (e.g., for a single product's details) or buy_product. No exclusion or alternative-routing guidance is given; usage must be inferred from sibling names and context.

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?

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds only 'free curated', which is minor context and does not meaningfully disclose return behavior, errors, or access requirements.

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 short sentence with no filler, and the main action verb is front-loaded. However, the brevity comes at the cost of useful detail, so it is concise but not fully informative.

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 one required parameter, no output schema, and no parameter documentation, the description is not complete enough for an agent to call the tool correctly. It does not say what the preview contains, what value to pass, or how this differs from list_products.

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% and the description never explains what the 'product' parameter should contain. There is no indication of whether product expects an ID, slug, name, or other identifier, leaving the only required parameter essentially undocumented.

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 ('Read') and resource ('free curated product preview'), so an agent can tell this is a read-only preview operation. It does not explicitly distinguish itself from siblings like list_products or buy_product, but the semantic difference is clear enough.

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 provides no guidance on when to use this tool versus alternatives such as list_products or buy_product. It does not state exclusions, prerequisites, or any routing logic.

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