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

Annotations already declare read-only, non-destructive, open-world, but the description adds genuinely non-obvious behavior: results are filtered by a user-managed allowlist at app.gscpap.com, so Google-permitted but disabled sites are invisible and unqueryable. It also discloses the exact shape of each entry and the four permissionLevel values, going beyond what the annotations convey.

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?

Front-loaded with the core purpose, then scope/filtering, then return shape, then sibling routing — a sensible order. The closing paragraph on GA4-vs-GSC question classes is slightly long for a list tool, though it does earn its place by preventing misrouting to the GA4 siblings.

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 zero-parameter, first-call discovery tool, everything needed is present: authorization scope, allowlist filtering semantics, returned fields, and routing to the GA4 counterpart. An output schema exists, and the description appropriately confirms rather than belabors return values.

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?

The tool takes zero parameters, so the baseline is 4; there is nothing for the description to disambiguate. It uses the space instead to document the returned fields (siteUrl, permissionLevel) rather than parameter meaning.

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 first sentence gives a precise verb and resource: 'List Google Search Console properties accessible to the authenticated user.' It also scopes the result to MCP-authorized properties, which distinguishes it from siblings that read GSC data (get_site_details, search_analytics_query) and from list_ga4_properties.

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?

It explicitly states the entry point ('the tool every client calls first') and names the alternative plus the condition that selects it: 'Call list_ga4_properties for those' (GA4 properties). It even sketches the question classes each source answers (sessions/conversions vs impressions/clicks/position) and points to correlate_gsc_to_ga4 for joins.

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