skylight_add_webcal

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

Annotations already declare readOnlyHint=false, destructiveHint=false, and openWorldHint=true, so the write/external nature is covered. The description's phrase 'subscribe the frame' adds the useful nuance that this creates an ongoing external subscription tied to a frame, but it says nothing about duplicate subscriptions, replacement behavior, or permissions. Adequate but thin against the annotation baseline.

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?

A single short sentence with the verb and target front-loaded and no filler. It is efficient, though it is arguably too terse to carry the guidance an agent needs.

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 mutating, open-world tool with an undocumented frameId and no output schema, the description leaves key operational questions unanswered: which frame is targeted by default, what happens if the URL is already subscribed, and whether Plus/subscription access is required. The one-sentence description is insufficient for this complexity.

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 50%: sync_url is documented in the schema, but frameId has no description anywhere. The description references 'the frame' without explaining how frameId is supplied, whether it is optional, or how a default frame is resolved, so it does not compensate for the coverage gap.

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 gives a specific verb and resource: 'Subscribe the frame to a webcal/ICS calendar URL.' An agent understands this adds an external calendar subscription. However, it does not distinguish itself from siblings such as skylight_create_source_calendar or skylight_link_apple_calendar, which sound like they do overlapping work.

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?

No when-to-use guidance, no prerequisites, and no mention of alternatives, despite several calendar-related siblings (create_source_calendar, link_apple_calendar, update_calendar) that an agent could easily confuse with this one. Usage must be inferred entirely from the name.

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