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

Beyond the readOnly/openWorld annotations it discloses quota cost (1 MCP credit per call), that summaries escape the section row allowance, the pricing multiplier after 500 credits/month, the consent requirement, and crucially that funnel contents are NOT returned but every row carries funnels_url. This is exactly the extra context annotations cannot carry.

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?

Dense and front-loaded: access gating first, then quota, then the funnels_url limitation, then pricing. The ALL-CAPS section labels make it scannable, but the description is long and a few clauses (e.g. the subscriber explanation) could be tightened.

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?

An output schema exists so return values need no explanation, yet the description still flags the one return-value nuance an agent must relay (funnels_url instead of funnel data). Combined with quota, consent and pricing prerequisites, an agent has everything needed to call it correctly and set user expectations.

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 is 3. The description restates the breakdown dimensions available (brand, category, domain, page, country, language, month) matching the group parameter and mentions 'with month range and filters', but adds no format or interplay details beyond 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?

States concretely that it returns a summary of the web2app (quiz-to-paywall) ad market from the Spytrend ad base, with the dimensions available (brand, category, domain, page, country, language, month). It is distinguishable from generic ad-search siblings by the explicit quiz-to-paywall framing, though it never names a sibling it competes with.

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?

Gives explicit preconditions and a workflow: the call is refused without the annual-plan add-on, a monthly 'site' subscriber is told MCP requires the annual plan, and the agent must call estimate_cost first and obtain accept_pricing_terms consent. It lacks explicit 'use X instead when Y' routing against siblings, so it falls 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.