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

Annotations already declare readOnlyHint=true, openWorldHint=true, and destructiveHint=false, and the description goes further by disclosing the report contents (top-3 expensive tools, size/pattern flags) rather than just restating that it reads. It omits any mention of auth requirements, rate limits, or whether the endpoint is actually contacted (network side effects of openWorldHint), leaving a small 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?

Two tight sentences: the first front-loads purpose and output shape, the second covers the two input modes. No filler, no redundant restatement of the title.

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 no output schema, the description carries the burden of describing returns and does so concretely (per-tool cost, top three, three flag categories). It does not specify the report format or units/scaling of the token estimate, which is a minor remaining gap for a low-complexity two-parameter read 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% and both parameters are already documented as 'Streamable HTTP MCP endpoint' and 'Tool definitions'. The description largely restates those, adding only the condition that the tools array is used 'if the server is not reachable over HTTP', which is a marginal gain over 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 a specific verb (Estimate) and resource (token cost of an MCP server's tools/list manifest), and enumerates the concrete outputs: per-tool cost, three most expensive tools, and flags for oversized descriptions, base64 blobs, and echoed schemas. An agent immediately knows what the tool produces; no sibling overlap exists to disambiguate.

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?

Implies the use case ('on every session start') and tells the caller how to invoke it in two modes: a live Streamable HTTP endpoint or a tools array. It does not name a when-not condition or point to an alternative, but the sibling tools (crawler checks, linting) are unrelated, so no routing guidance is genuinely needed.

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