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

Annotations already declare readOnly/idempotent/non-destructive/openWorld=false, so the safety profile is covered. The description adds genuine value beyond that: what a result contains (forms with images, what to look for, confusable letters, copybook plates 'where FamilyLore has them') and the degradation behavior when only a hand is supplied (returns that hand's alphabet).

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 resource and scope, and the sentence-per-idea structure (what it returns, when to use, how to supply the letter, fallback, exclusion) is efficient. It is dense and list-heavy, but almost every clause carries usable routing or input information.

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?

An output schema exists so return format needn't be spelled out, and despite both parameters being optional the description explains the hand-only fallback and the letter forms accepted. Nothing an agent needs in order to call this correctly is missing.

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% and the schema already states the letter may be given as written (ѣ, G, ך), by name (yat, alef), or transliterated, and lists the five hands. The description largely restates this, adding only mild context (letter optional, hand 'if known'), so the baseline 3 applies.

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?

Starts with a concrete verb+resource ('guide to the 137 letters of five old handwriting styles') and enumerates the specific hands covered. An agent can tell this apart from read_letter/ask_letter immediately: this explains alphabets, it does not read documents.

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?

Explicit trigger conditions are given ('when someone asks how a letter was written... what an old letter shape is, or why two letters look alike') plus an explicit exclusion ('Do not use it to read a letter or photo the person has'), which effectively routes the agent to the reading siblings.

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