skim402

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

Annotations declare readOnlyHint=true and openWorldHint=true, aligning with the description. Beyond annotations, the description adds valuable context: the per-call cost ($0.015 USDC via x402) and the hard dependency on a wallet configured in the X-Skim-Wallet-Key connector header. It also notes the schema must have top-level type 'object'.

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, front-loaded with the core action and the two input modes, then packed with cost/wallet prerequisites. Zero filler words; every clause earns its place.

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?

Well-covered for a tool with full schema coverage, read-only annotations, and no output schema. The description handles the mutually-exclusive parameters, cost, and auth prerequisite. Missing a note about expected return shape given no output schema, but annotations plus description make it adequately usable.

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 100%, so the schema documents all 4 parameters. The description adds marginal value by explaining the preset-vs-schema mutual exclusivity and the top-level type 'object' constraint that isn't in the schema. It does not detail the schema format further, but baseline 3 is appropriate given full coverage.

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?

Description uses specific verbs ('read', 'extract structured JSON') plus resource ('web page via Skim'). Clearly distinguishes from siblings (skim_read reads page content; this extracts structured JSON). Lists preset names and schema option explicitly.

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?

Clearly explains the two mutually exclusive input modes (preset vs schema) and how to choose ('Either pick a preset...or supply a JSON Schema'). Notes cost and wallet requirement as prerequisites. Does not explicitly name sibling alternatives for when to use one vs another, so not 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?

Annotations already declare readOnlyHint=true and openWorldHint=true, covering the safety profile. The description adds value by disclosing rate-limiting, the paid-wallet alternative, and exact pricing ($0.002 on Base via x402), plus what it strips (nav, ads, boilerplate), going beyond what annotations provide.

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?

Three sentences, all earning their place: purpose, content types, and pricing/rate-limit notes. No wasted words, well front-loaded with the primary action first. Could trim slightly but it's efficient for an API with billing implications.

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?

Simple one-param tool with full schema coverage and readOnly/openWorld annotations handles most completeness burden. The description adds the non-obvious context (Skim provider, rate limiting, x402 payment mechanism, return format as recognized Markdown) without fluff, making it complete for a simple fetch 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 coverage is 100% with a single url parameter well documented. The description compensates by clarifying the URL must be public, enhancing what the schema format:uri implies with provider expectations (public fetchable content). With full schema coverage and one simple param, baseline is 3 elevated to 4.

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?

Clear verb+object ('Fetch... return clean, agent-ready Markdown') plus explicit list of content types (articles, docs, blog posts, READMEs, research papers). Describes what gets stripped vs preserved, which differentiates it meaningfully from siblings like skim_extract and skim_signals.

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?

Clearly states what content it's for and highlights the free-tier rate limit plus paid unmetered option via X-Skim-Wallet-Key. Names the service (Skim 402) giving context on cost/limits, though it doesn't explicitly contrast against skim_extract/skim_signals by name.

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 and openWorldHint=true, so the safety profile is well covered. The description adds value by disclosing the explicit per-call cost ($0.005 USDC), the required X-Skim-Wallet-Key connector header, and that calls fail without one. However, it doesn't describe edge behaviors like rate limiting, pagination beyond the limit parameter, or error responses, leaving some gap given openWorldHint.

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 tight two-sentence structure that front-loads the primary purpose in the first sentence, followed by the pricing/authentication caveat. Every clause earns its place, and the enumerated feed list is compactly inline rather than expanded into wasteful prose. Minor room for improvement in structural separation of the caveat, but overall 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 feed-list tool with readOnlyHint=true, complete schema coverage, and no output schema, the description adequately covers the purpose, the pricing model, and the hard authentication requirement. It falls slightly short of a 5 because it doesn't mention expected value shapes of returned items or any ordering/count caveats beyond 'newest first', but it's genuinely complete for 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?

Schema description coverage is 100%, so the schema fully documents both parameters (signal enum with all 18 values and limit with min/max/default). The description does not add syntax or format details for the parameters beyond what the schema provides, so the baseline of 3 is appropriate. The schema carries the heavy lifting.

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 gives a specific verb ('Fetch') plus resource ('Skim's curated intelligence feeds'), names the exact URL (skim402.com/signals), and lists all 18 available signal categories at the call site. It clearly distinguishes this from the sibling tools (skim_extract, skim_read) by framing it as a feed-fetching operation. This is a precise, unambiguous statement of what the tool does.

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 that it fetches 'latest items' from curated feeds and that results are returned 'newest first', giving clear usage context. It does not explicitly state when-not-to-use or name alternatives, though the sibling separation is implicit from the different verbs. It notes the cost per call and hard dependency on a wallet connector, which is valuable pre-usage guidance.

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