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

With readOnlyHint=false and idempotentHint=false already declared, the description still adds real substance: it is a paid, balance-funded mutation, the current call bills the first month of each new block, pricing is $5/block/month, and data above the allowance is counted but discarded. That explains the non-idempotent billing behavior far beyond what the annotations say.

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 pricing is stated twice ('at $5 a month each' and 'Costs $5.00 per block of a million events a month'), and 'nothing if none are found' is ambiguous filler. Front-loading of the core action is good, but a sentence is wasted on restated pricing.

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 2-parameter paid mutation with no output schema, the description covers cost, billing source, first-month charge, and overage consequences. Gaps remain around permission requirements, whether blocks are ever removed/downgraded, and what the call returns, but the essentials for correct invocation are 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 50% — `site` is documented in-schema but `blocks` is a bare integer. The description compensates by defining the unit of a block (one million events) and its price, which is the key semantic an agent needs. It does not mention the 1–20 bounds, which remain schema-only.

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-and-resource pair: it raises a site's monthly event allowance in blocks of a million. It clearly distinguishes this call from analytics_add_site / analytics_update_site by describing an allowance-purchase action, but it never names those siblings 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?

Usage is implied by the causal chain — events above the allowance are counted but not stored, so you call this when you need to store more. There is no explicit 'use this when' statement, no exclusions, and no named alternative (e.g., analytics_update_site, analytics_remove_site) to contrast with.

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