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

Annotations already cover safety (readOnly/idempotent/destructive=false), and the description adds real value beyond them: the data is static and weekly, coordinates are source points rather than geocoded market locations, and maps_url is a search link, not a precise pin. That preempts several likely agent misreadings. It says nothing about pagination or data freshness/update cadence, keeping it out of the 5 band.

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?

Three short, front-loaded sentences with no filler: scope first, parameter format second, interpretation caveats last. The coordinates/maps_url sentence is slightly tangential but still earns its place as a usage caveat.

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 an output schema present, return values needn't be described, and the key interpretive caveats are covered. The remaining gap is the undocumented `limit` parameter and district matching rules, which matters for a 3-parameter tool with no schema descriptions.

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 0%, so the description carries the burden. It does this well for `day`, enumerating accepted formats (Turkish/English weekdays, today/yesterday/tomorrow, ISO date), and implies `district`. But `limit` is never mentioned and `district` matching semantics (exact name? case-insensitive? Turkish characters?) are unstated, so compensation is only partial.

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 and resource — returns the published weekly İBB market schedule — plus the optional scoping dimensions (district/day). This clearly separates it from siblings like istanbul_nearby or istanbul_query_resource, which cover different data domains.

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?

The line 'Results are a static weekly schedule, not proof a market is open today' is an explicit when-not-to-rely-on-it caveat, which is strong guidance. It doesn't name a sibling alternative for live market status, so it stops short of the top band.

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