UK EPC MCP

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

With no annotations, the description carries the full behavioral burden. It does disclose a 5-result cap, which is genuinely useful, but adds nothing about auth, rate limits, or whether the 'free' quota is per-session or per-key. 'Soft-Offer outbound is OFF' is opaque internal jargon that conveys no behavior an agent can act on.

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?

It is short, but brevity here comes from omission rather than economy. The opening 'Free peek, max 5' and the trailing 'Soft-Offer outbound is OFF' are cryptic fragments that consume the front-loaded position without telling the agent anything actionable.

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 two parameters, no output schema, and no annotations, the description should explain the return shape and the meaning of the result cap. It instead leaves the size semantics, quota behavior, and output content entirely undocumented, so an agent cannot call this confidently beyond a bare postcode query.

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 only 50% and the postcode description ('Example EC1') is thin. The 'size' parameter is never mentioned in the description, and it is unclear whether 'max 5' overrides size or whether size means result count, page size, or record size. The description does not 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?

The core resource is stated clearly: domestic Energy Performance Certificates for a postcode in England and Wales. However, the leading fragment 'Free peek, max 5' is unexplained jargon and no verb tells the agent what 'discover' actually does (list? search? sample?). Nothing distinguishes it from the sibling epc_pack beyond an implicit free-vs-paid hint.

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?

'Free peek, max 5' implies this is a trial/sample call rather than a full retrieval, and the England-and-Wales scope implicitly excludes other regions. But the description never says when to use this instead of epc_pack or how redeem_pack relates, leaving the routing decision to inference from the tool names.

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 behavioral burden and does provide useful context: it returns a Stripe Checkout URL, costs £0.49, is limited to England and Wales, and has 'Soft-Offer outbound is OFF'. However, it omits authentication needs, side effects, payment lifecycle, and error conditions.

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 short and front-loaded: paid pack, return value and price, geographic scope, and an operational flag. The final sentence is cryptic but does not make the definition verbose.

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 annotations, no output schema, and 0% schema description coverage, the definition leaves important gaps. It explains the checkout URL and price but not the size parameter, usage routing, or key behavioral prerequisites for a paid tool.

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 must explain the two parameters. It gives geographic context for postcode but does not define its format, and it does not mention the size parameter at all.

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 paid pack for Domestic Energy Performance Certificates by postcode in England and Wales, and says it returns a Stripe Checkout URL at £0.49. That is clear enough to identify the tool's action and resource, but it does not explicitly distinguish it from siblings such as epc_discover or redeem_pack.

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?

There is no explicit guidance on when to use this tool versus epc_discover or redeem_pack. 'Paid pack' implies a purchase flow, but the description does not state prerequisites, alternatives, or when not to use it.

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 disclosure burden. It says nothing about side effects (does it grant entitlements or credit a pack?), idempotency on repeated redemption, error behavior for unpaid/invalid sessions, or required auth, all of which are essential for an unreversible-sounding redemption operation.

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?

It is short, but brevity here comes from under-specification rather than efficiency; a single fragmentary sentence that reads like a heading and conveys almost nothing front-loaded.

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 mutation-style tool with zero annotations, no output schema, and an undocumented required parameter, the description provides none of the context needed to invoke it correctly or interpret the result.

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 single required parameter session_id is completely undocumented in the description. The agent gets no indication that the identifier is a Stripe Checkout session ID, what format it takes, or how to obtain 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 text reads as a title fragment ('How to redeem...') rather than a statement of what the tool does. It gestures at the resource (a paid Stripe Checkout session) but never says the tool actually performs the redemption or returns anything, leaving the verb ambiguous.

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?

Mentioning 'paid' implies this only applies to completed checkout sessions, which is a faint usage cue. But there is no explicit when-to-use, no prerequisites, and no reference to the sibling tools epc_pack or epc_discover, which are plausible alternatives an agent would need to disambiguate against.

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