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

Annotations already establish a safe read-only, closed-world operation, and the description adds meaningful domain behavior: the fast day depends on the tithi at local sunrise, the fast-breaking window is minutes-wide and city-specific, and each observance links to a story/verse page. It does not describe response format or pagination details, but it adds substantial context beyond the annotations.

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 short paragraphs with no wasted text. The primary purpose and the critical location constraint are front-loaded, and each sentence contributes either routing guidance or essential behavioral context.

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 six-parameter read-only calendar tool with no output schema, the description covers purpose, when to use it, location requirements, and the nature of returned links. It does not mention the days or language parameters, but those are fully documented in the schema and are secondary to correct invocation.

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%, so the baseline is 3. The description goes beyond the schema by explaining why latitude, longitude, and timezone are required and consequential—local sunrise determines the fast day and the break-fast time differs by city—which helps the agent avoid guessing a location.

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 names a specific resource (Ekadashi fasts, festivals, acharya appearance/disappearance days) and a specific computation scope ('computed for one place'). It is immediately distinguishable from all listed siblings, which are text/verse browsing tools.

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 gives clear triggering conditions: any question about when an Ekadashi or festival falls, or when to break a fast. It also advises asking the user for their location rather than guessing. It lacks explicit when-not-to-use guidance or named alternatives, but the sibling set makes overlap unlikely.

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