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

Goes well past the annotations (which already say readOnly, non-destructive, closed-world) by disclosing counting semantics ('activity is counted at most once a minute, so this is sessions-ish, not page views'), the meaning of a missing first_opened, the domain-row/`via` row structure, and the public-project coverage gap. These are exactly the behavioral traits an agent cannot get from structured fields and would otherwise misreport.

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 core ('who opened it, when, how many') is front-loaded, and most sentences carry real semantic payload. It is delivered as one dense run-on block with several parenthetical asides, so a slightly more segmented structure would improve scannability, but there is little filler.

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?

Even though an output schema exists, the description adds the interpretive layer needed to read it correctly (sessions-ish counting, domain rows, unopened invites). Combined with the stated coverage limits, an agent has everything needed to call it and to caveat the results appropriately.

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?

A single required parameter with 100% schema description coverage ('the id of the project to fetch'), so the schema already does the work. The description adds no syntax, format, or lookup guidance for project_id, which is acceptable but not a value-add — baseline 3 applies.

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?

Opens with a specific verb and resource: 'Report who has opened a spawnpoint project, per invited email', then enumerates exactly what is returned (opened status, first/last RFC3339 timestamps, visit count). It never names a sibling, so the distinction from get_project_logs or get_project has to be inferred from the analytics framing rather than stated.

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 a clear decision context: 'for a restricted project this is the complete answer to "did they look at it"', which tells the agent when this tool is the right call. It also states the exclusion (a public project's anonymous traffic is not collected), though it does so as a data limitation rather than an explicit 'use X instead' routing rule.

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