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

Annotations already cover read-only and non-destructive behavior. The description adds meaningful behavioral detail on top: positions are 'Calculated at noon UTC,' the time-source makes limits, and the default-current-month behavior is explained. It adds genuine context beyond the annotations without contradicting them.

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 first few sentences are clear and front-loaded. However, the description ends with a redundant keyword-stuffed sentence: 'Monthly planetary ephemeris API, syderial position table, daily graha gochara positions, ecliptic longitude calculator.' This sentence repeats already-stated concepts and adds noise without earning its place.

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?

The description covers key return fields, calculation time, default behavior, and the tool's main use cases. There is no output schema, but the listed return values and daily-monthly scope give enough for an agent to understand the response shape. It is sufficiently complete for a read-only data-lookup 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 description coverage is 100%, so the input schema already fully documents all five parameters. The description only reinforces the default behavior by explaining 'Omit year and month to get the month in progress,' which is marginal extra value. It does not clarify compact, lang, or coordinateSystem beyond the schema, so the baseline 3 is appropriate.

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 starts with a very specific verb/resource: 'Get daily sidereal ecliptic positions for all 9 Vedic planets (Navagraha) for an entire month.' It clearly states what data is returned (longitude, sign, degree, retrograde status), making the tool's function easy to identify. It does not explicitly name or contrast a sibling tool like post_vedic_astrology_planetary_positions, so it misses the full 5 by just a bit.

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 description provides clear use context: 'Essential for ephemeris generation, transit tracking, and planetary movement visualization.' It also gives a practical usage tip about omitting year and month to keep a published ephemeris page current. However, it lacks explicit when-not-to-use guidance or a contrast with alternative monthly tools, such as transit_monthly.

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